Grid for battery plate, method of producing the same, and battery using the same

ABSTRACT

A grid for a battery plate is made by forming a metal sheet is formed into a grid-like shape. Rupture due to torsion or stress concentration does not occur in a basal portion of a wire which is drawn out from a node of the grid, thereby preventing corrosion due to electrolyte from advancing so as not to cause a crack of corrosion in an early stage. The invention provides also a battery using the grid for a battery plate, a method of producing the grid for a battery plate, and a battery using it.

REFERENCE TO RELATED APPLICATION

This is a divisional application of Ser. No. 12/011,372, filed Jan. 25,2008, which is now issued on Oct. 19, 2010, as U.S. Pat. No. 7,814,628,which is a divisional of Ser. No. 10/177,972 filed Jun. 20, 2002, nowabandoned. The subject matter of the aforementioned prior applicationsare hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a grid for a battery plate which isproduced by a rotary expander, a method of producing it, and a batteryusing it.

A battery plate of a lead storage battery is configured by filling anactive material into meshes of a grid made of lead or a lead alloy. Sucha grid is often produced by directly forming a grid-like shape by meansof, for example, casting of lead or a lead alloy, or alternatively byforming meshes in a metal sheet made of lead or a lead alloy(hereinafter, a sheet such as that containing lead, a lead alloy, oranother alloy is referred to merely as a metal sheet) by an expander.The expander is of the reciprocal type in which meshes are sequentiallyformed in a metal sheet with starting from both the ends of the sheet,by vertical motions of a die cutter, or of the rotary type in whichslits are formed in a zigzag pattern by rotation of a disk cutter, andthe metal sheet is stretched from both the sides to develop the slitsinto meshes. As shown in FIG. 37, in a disk cutter 1 which is used inthe rotary expander, large numbers of ridges 1 a and valleys 1 b arealternately formed at regular intervals along a circumferentialdirection on the peripheral side face of a metal disk. The valleys 1 bare curved faces consisting of the circumferential face itselfconstituting the peripheral side face of the disk of the disk cutter 1.The oval enlarged view in FIG. 37 shows the circumferential face in aform developed to a plane. Each of the ridges 1 a is formed byprotruding the circumferential face of the disk cutter 1 in a ridge-likeshape toward the outer periphery. The apex of the ridge is rounded andformed with being shifted toward the front side in the rotationaldirection (indicated by the arrow in the figure).

In the disk cutter 1, grooves 1 c are formed in both the disk-like facesand in every other valley 1 b. Each of the grooves 1 c is a groove whichhas a width that is equal to the length (the distance between adjacentridges 1 a) of the corresponding valley 1 b, and a depth that is aboutone half of the thickness of the valley 1 b (the thickness of the diskcutter 1), and which is radially formed in the disk face of the diskcutter 1. The groove 1 c is formed so as to open in the valley 1 b inthe outer peripheral side and have a length of some degree toward thecenter. The grooves 1 c which are formed in every other valley 1 b arearranged so as to be alternate on both the faces.

A large number of such disk cutters 1 are arranged on a common rotationshaft with being separated from each other by a distance which isapproximately equal to the thickness of the disk cutters 1, therebyforming a disk cutter roll. As shown in FIG. 38, two disk cutter rollseach configured by a large number of such disk cutters 1 are verticallyarranged, and a lead sheet 2 is passed between the rolls, therebyforming slits 2 a. In this case, as, shown in FIG. 39( a), the upper andlower disk cutter rolls are placed respectively at levels which allowthe valleys 1 b of the upper and lower disk cutter 1 to slightly overlapwith each other. Furthermore, the upper and lower disk cutter rolls areplaced with being shifted in the axial direction by a half pitch so thateach of the disk cutters 1 of the lower disk cutter roll is positionedbetween the disk cutters 1 of the upper disk cutter roll. The rotationalphase is adjusted so that, when the valley 1 b in which the groove 1 cis formed in one disk face of the upper disk cutter 1 reaches the lowerend, the valley 1 b in which the groove 1 c is formed in the other diskface of the lower disk cutter 1 reaches the upper end, and, when theridge 1 a of the upper disk cutter 1 reaches the lower end, as shown inFIG. 39( b), the ridge 1 a of the lower disk cutter 1 reaches the upperend.

When a metal sheet 2 is passed between the disk cutter rolls, as shownin FIG. 38, the slits 2 a are formed in the metal sheet 2 by the ridges1 a of the upper and lower disk cutters 1, and thin wires 2 b betweenthe slits 2 a which are formed adjacently in the width direction of themetal sheet 2 are pressed by the upper and lower ridges 1 a toalternately vertically protrude in a ridge-like shape. As shown in FIG.39( a), in the valleys 1 b of the upper and lower disk cutters 1 wherethe grooves 1 c face each other in opposite directions, the metal sheet2 is cut so that the slits 2 a are continuously formed, and, in thevalleys where the grooves 1 c face each other, the metal sheet 2 is notcut so that the slits 2 a are intermitted to form nodes 2 c. In themetal sheet 2, therefore, the slits 2 a each having a lengthcorresponding to two ride-like shapes which are formed by pressing ofthe ridges 1 a are continuously formed in the transportation directionwhile being intermitted in the nodes 2 c. Adjacent ones of the slits 2 aare similarly continuously formed while their nodes 2 c are shifted fromeach other by a half pitch. Therefore, the slits 2 a are formed in azigzag pattern as shown in a plan view which is in a circle of FIG. 38.

The metal sheet (lead sheet) 2 in which the many slits 2 a are formed asdescribed above is stretched toward both the sides in the widthdirection in a subsequent step. As a result, as shown in FIG. 40, theslits 2 a are widened so as to form meshes, whereby a lattice-like gridis formed in which the nodes 2 c are connected to one another by fourwires 2 b that are obliquely bent to be drawn out.

As shown in FIG. 47, endmost disk cutters 4 are disposed on both theaxial ends of the lower disk cutter roll, respectively. In each of theendmost disk cutters 4, as shown in FIGS. 48 and 49, ridges 4 a andvalleys 4 b are alternately arranged in the peripheral edge. The valleys4 b, and grooves 4 c which are formed in the valleys 4 b are configuredin the strictly identical manner as the valleys 1 b and the grooves 1 cof the usual disk cutters 1. In each of the ridges 4 a, however, aperipheral side face configured by a reference circumferential face isformed. Namely, in the endmost disk cutters 4, the ridges 4 a do notprotrude in a ridge-like shape toward the outer periphery, and thevalleys 4 b do not have a shape which is relatively recessed withrespect to the ridges 4 a. The endmost disk cutters 4 are placed at theends of the lower disk cutter roll so as to be outward juxtaposed withthe usual disk cutters 1 at the ends of the upper disk cutter roll,respectively.

In the ends of the disk cutter rolls, as shown in FIG. 47( b), theridges 4 a of the endmost disk cutters 4 of the lower disk cutter rolloverlap with the ridges 1 a of the end disk cutters 1 of the upper diskcutter roll, whereby the metal sheet 2 between the ridges are cut sothat the slits 2 a are formed and the wires 2 b downward protrude in aride-like shape. As shown in FIGS. 47( a) and 47(c), also in theadjacent portions (the right end in FIG. 47( a), and the left end inFIG. 47( b)) where the grooves 4 c of the valleys 4 b of the lowerendmost disk cutters 4, and the grooves 1 c of the valleys 1 b of theupper end disk cutters 1 face each other in opposite directions, thevalleys 1 b and 4 b slightly overlap with each other, whereby the metalsheet 2 is cut and the slits 2 a are continuously formed. However, inthe adjacent portions (the left end in FIG. 47( a), and the right end inFIG. 47( b)) where the grooves 4 c of the valleys 4 b of the lowerendmost disk cutters 4, and the grooves 1 c of the valleys 1 b of theupper end disk cutters 1 are formed in the opposed faces so as to faceeach other, the grooves 1 c and 4 c cause the peripheral side faces ofthe valleys 1 b and 4 b not to overlap with each other, and the metalsheet 2 is not cut. Therefore, endmost nodes 2 f which are similar tothe nodes 2 c are formed. Since no slit 2 a is formed in the outer end,the endmost nodes 2 f are directly connected to frame portions 2 g whichare formed in the ends in the width direction of the metal sheet 2.

The metal sheet 2 in which the many slits 2 a are formed as describedabove is stretched toward both the sides in the width direction in thesubsequent step of the rotary expander. As a result, as shown in FIG.50, the slits 2 a are widened so as to form meshes, whereby alattice-like grid is formed in which the nodes 20 and the endmost nodes2 f are connected to one another by four wires 2 b that are obliquelydrawn out. In practice, the nodes 2 c are pulled by the wires 2 b duringthe developing step to be inclined in a twisting direction. In FIG. 50,however, such twist is omitted and the grid is diagrammatically shown.

Problem (1) to be Solved by the Invention

In the conventional grid described above, when the slits 2 a are formedin the metal sheet 2, the wires 2 b connected to each of the nodes 2 care pressed by the ridges 1 a to be bent in the basal end. During aprocess of developing the slits 2 a into a lattice-like shape, thetensile stress applied to the wires 2 b is concentrated in the basal endwhere the wires are connected to the node 2 c. When stress isconcentrated in the basal end of the node 2 c, an excessive load isapplied to the basal end during the developing process, and rupture mayoccur in the basal end. Therefore, corrosion due to electrolyte easilyadvances with starting from the basal end, thereby causing thepossibility that a crack of corrosion occurs in the wires 2 b during useof a battery.

Consequently, a conventional grid which is produced by using a rotaryexpander has a problem in that a basal end where a wire is connected toa node is cracked by corrosion and the life of a battery is shortened.

Problem (2) to be Solved by the Invention

In the conventional disk cutter 1 configured as described above, asshown in FIG. 41, each of the ridges 1 a is not formed as a ridge havingan isosceles triangular shape, but formed into a scalene triangularshape in which the apex 1 i is formed with being shifted toward thefront side in the rotational direction. The rotating disk cutter 1 formsthe slits 2 a in the metal sheet 2, and presses the fence-like portionbetween the slits 2 a by the ridges 1 a to project the portion in aridge-like shape, thereby forming the wires 2 b. In the case where theridges 1 a have an isosceles triangular shape, therefore, the front halfof the fence-like portion between the slits 2 a protrudes in aridge-like shape while being gradually stretched by the apexes 1 i ofthe ridges 1 a, and in contrast the latter half is pressed only by therear slopes of the ridges 1 a which are in rear of the apexes of theridges 1 a. In each of the wires 2 b between the slits 2 a andprotruding in a ridge-like shape, consequently, the front half is moreelongated to be thinned. When a grid is formed by stretching such wires,there arises a defect that walls of the meshes are uneven in thickness.By contrast, when the apex 1 i of each ridge 1 a is formed with beingshifted toward the front side, the fence-like portion between the slits2 a is first pressed by a substantially whole front area of the slopewhich is raised by a steep angle θ₁₀ of the front side, so as toprotrude at a relatively early timing to form the wires 2 b. Inaccordance with the rotation, also the rear area gradually protrudes. Asa result, the whole wires 2 b are uniformly extended and the thicknessis even. Because of the above, conventionally, a rotary expander usesthe disk cutter 1 in which the apex 1 i of the ridge 1 a is formed withbeing shifted toward the front side in the rotational direction (seeJapanese Patent Publication (Kokoku) No. SHO59-35694).

The metal sheet 2 in which the many slits 2 a are formed as describedabove is stretched toward both the sides in the width direction in asubsequent step, whereby the slits 2 a are widened to form rhombicmeshes, with the result that a grid for a battery plate is formed.

With respect to the angles at which the slopes on both the sides of theapex 1 i of each ridge 1 a are connected to the valleys 1 b, the frontangle θ₁₀ is steeper than the rear angle θ₂₀. As shown in FIG. 42, alsoin each of the wires 2 b which are formed as a result of protrusion ofthe fence-like portion between the slits 2 a of the metal sheet 2 in aridge-like shape, therefore, the front bending angle θ₁₁ is steeper thanthe rear bending angle θ₂₁. When the metal sheet 2 is stretched to widenthe slits 2 a to form meshes, therefore, the degree of cut into thenodes 2 c is large or the strength is reduced in the front end where thewires 2 b between the slits 2 a are sharply bent. As a result, as shownin FIG. 43, there arises the possibility that the length of the nodes 2c is reduced, or rupture occurs in edge portions (edge portions D inFIG. 43). In FIG. 43, twisting is not shown, and the grid isschematically shown.

When a grid for a battery plate is produced by using the disk cutters 1of a conventional rotary expander, particularly in the case where thegrid is used as a positive plate, the nodes 2 c of the meshes and theedge portions D are corroded by electrolyte with starting from ruptureor the like to cause a crack of corrosion, thereby producing a problemin that the capacity of a lead storage battery is reduced or the life ofthe battery is shortened.

Problem (3) to be Solved by the Invention

As shown in FIG. 44, the wires 2 b are pressed by the ridges 1 a of thedisk cutters 1 to be elastically deformed in a ridge-like shape in whichthe apex 2 e is bent at the steepest curvature. Even when the ridges arestretched in an oblique direction in the developing step to becomelinear, therefore, the apex 2 e of each ridge remains to be elasticallydeformed and hence cannot be stretched into a fully linear form. Whenthe wires 2 b are stretched in the developing step, consequently, thetensile stress in this process is easily concentrated in both sides ofthe elastically deformed portion of the apex 2 e which is bent.

In practice, the wires 2 b are developed in the developing step not onlyby being obliquely stretched to become linear, also by being twisted atthe ends in opposite directions as indicated by the arrows D and E inFIG. 45. As shown in FIG. 39( a) or FIGS. 47( a) and 47(c), in each ofthe nodes 2 c, the sides in the width direction of the metal sheet 2 arevertically pressed in opposite directions by the valleys 1 b of theupper and lower the disk cutters 1. Therefore, a level difference whichapproximately corresponds to the thickness of the sheet is formedbetween one side in the width direction and the other side, and alsopositions where the wires 2 b are drawn out are different in level. Asshown in FIG. 45, in a node 2 c which is connected to one end of acertain wire 2 b, one side in the width direction is higher in level,and the other side is lower. By contrast, in another node 2 c which isconnected to the other end of the same wire 2 b, one side in the widthdirection is lower in level, and the other side is higher. When themetal sheet 2 is stretched in the width direction, therefore, the nodes2 c are stretched toward both the sides in the width direction by thewires 2 b which are different in level, with the result that the nodes 2c, 2 c which are shown in right upper, and left lower portions of FIG.45 are twisted in the direction of the arrow F, and in contrast thenodes 2 c, 2 c which are shown in left upper, and right lower portionsof FIG. 45 are twisted in the opposite direction or the direction of thearrow G. The wire 2 b between the right upper and left upper nodes 2 c,2 c is developed while the ends are twisted in opposite directions orthe directions of the arrows D and E, respectively. As a result, each ofthe wires 2 b is stretched while the ends are twisted in oppositedirections, so that the torsion stress is easily concentrated in bothsides of the elastically deformed portion of the apex 2 e.

In each of the wires 2 b, consequently, the tensile stress and thetorsion stress in the developing step are concentrated on both the sidesof the elastically deformed portion of the apex 2 e which remains to bebent, and a constricted part may be formed. Therefore, a grid which isproduced by using a conventional rotary expander has a problem in thatrupture often occurs in the portion. In the case where the metal sheet 2is thick or has a thickness larger than 1.0 mm, or the case where thedisk cutters 1 in which the ridges 1 a largely protrude are used,particularly, rupture often occurs in the vicinity of the apex 2 e ofeach wire 2 b. When a battery is produced by using such a grid as abattery plate, local corrosion occurs in the rupture portion, or in theworst case a crack of corrosion occurs the wires 2 b, thereby causingthe life of the battery to be shortened. The invention has beenconducted in order to cope with the above-discussed circumstances. It isan object of the invention to provide a grid for a battery plate inwhich an inclined face is formed on a peripheral side face of each ridgeof a disk cutter, and wires are formed in a ridge-like shape in a statewhere the wires are pretwisted, thereby causing the wires to hardlyrupture, and also a method of producing the grid.

Problem (4) to be Solved by the Invention

The shape of the disk cutter 1 and production steps in the production ofa grid for a battery plate in which disk cutters for a rotary expanderare used are shown in FIGS. 37 to 40. In a process of producing the gridfor a battery plate, the slits 2 a and the nodes 2 c are formed in themetal sheet 2. As apparent from FIG. 46( a), the cutting is conductedwhile pressing each of the nodes 2 c against a ridgeline 1 k of theportion of the disk cutter 1 where the groove 1 c of the peripheral sideface of the valley 1 b is formed. As shown in FIG. 46( b), therefore,stress is concentrated on the portion against which the ridgeline 1 k ispressed, and rupture sometimes occurs in the node 2 c. When such ruptureonce occurs, corrosion advances with starting from the rupture, andcrack of corrosion finally occurs, thereby producing a problem in thatthe capacity of a lead storage battery is reduced or the life of thebattery is shortened.

The invention has been conducted in order to cope with theabove-discussed circumstances. It is an object of the invention toprovide a method of producing a grid for a battery in which stressconcentration is relaxed and rupture hardly occurs in the node 2 c, anda battery using the grid for a battery.

Problem (5) to be Solved by the Invention

In the formation of the nodes 2 c and the endmost nodes 2 f of the metalsheet 2, as shown in FIGS. 47( a) and 47(c), the sides in the widthdirection are vertically pressed in opposite directions by the valleys 1b and 4 b of the upper and lower disk cutters 1 and the endmost diskcutters 4 in which the grooves 1 c are opposed to each other. Therefore,the sides in the width direction are vertically deformed with respect toeach other by a large degree corresponding to the thickness of the metalsheet 2 or more, and the metal sheet 2 of the endmost nodes 2 f isstretched to be thinned in accordance with the deformation. When themetal sheet 2 is stretched toward both the sides in the width direction,development is conducted while the wires 2 b drawn out from the nodes 2c and the endmost nodes 2 f which are thinned by the verticaldeformation are laterally pulled to be obliquely bent. Therefore, stressis concentrated on the nodes 2 c and the endmost nodes 2 f, and thepossibilities that rupture occurs during a production process, and that,after a battery is produced by using such a grid for a battery, a crackof corrosion is caused between the nodes and the wires 2 b by corrosionor heat are increased. When a crack of corrosion of the wires 2 b occursin one of the endmost nodes 2 f connected to the frame portions 2 g ofthe metal sheet 2 where a lug of the grid is formed for currentcollection from the battery plate, the plate portion that is on theother side in the width direction is connected to the lug through adetour. As a result, the current hardly flows, so that disadvantagessuch as that the active material in the portion is not effectively used,and that a large current flows through the detour to generate heat arelargely increased. When a crack of corrosion occurs in any one of thenodes 2 c other than the endmost nodes 2 f, similarly, a current hardlyflows from the plate portion that is on the other side in the widthdirection with respect to the node 2 c. However, influence due to theabove is more extremely reduced as the node 2 c is more separated fromthe frame portions 2 g where a lug is formed.

SUMMARY OF THE INVENTION

The invention has been conducted in order to solve the above-discussedproblems. It is an object of the invention to provide a grid for abattery plate in which various unique measures are taken mainly on theperipheral side faces of the valleys 1 b between the ridges 1 a of thedisk cutters 1, to prevent rupture from occurring during a process ofproducing the grid, and corrosion and a crack of corrosion fromoccurring in nodes and edges of meshes of the grid for a battery plate,thereby preventing the capacity of a lead storage battery from beingreduced, and the life of the battery from being shortened, a method ofproducing the grid, and a battery using the grid.

In the endmost nodes 2 f connected to the frame portions 2 g of themetal sheet 2, a crack of corrosion of the wires 2 b easily occurs inthe same manner as in the other nodes 2 c. Consequently, there arises aproblem in that, in many batteries, the capacity is largely reduced by acrack in the endmost nodes 2 f. The invention has been conducted inorder to cope with the above-discussed circumstances. It is an object ofthe invention to provide a grid for a battery plate in which theperipheral side faces of the valleys of the endmost disk cutters arerecessed toward the center, whereby deformation of endmost nodes isreduced so that a crack of wires hardly occurs, and a method ofproducing the grid.

Means for Solving Problem (1)

The invention provides a grid for a battery plate in which a largenumber of slits each configured by a cut elongating in a longitudinaldirection are formed in a metal sheet in a zigzag pattern, the metalsheet is stretched in a width direction to develop the slits, and nodesconfigured between slits that are adjacent in the longitudinal directionare connected to one another to form a lattice-like shape, by four wireswhich are configured between slits that are adjacent in the widthdirection, and which are obliquely bent to be drawn out, wherein

at least one of the four wires connected to each of the nodes is bent ina predetermined oblique direction via a drawn-out portion which is drawnout from the node in a substantially longitudinal direction.

According to the invention, since at least one wire is bent at the tipend of the substantially straight drawn-out portion which is drawn outfrom the node, tensile stress produced during a process of developingthe wire is applied with being dispersed not only to the basal end ofthe node but also to the whole drawn-out portion, and hence at least thewire can be prevented from being easily corroded.

The invention provides a method of producing a grid for a battery platein which a metal sheet is passed between two rotating disk cutter rollsin each of which a plurality of disk cutters are placed on a same shaftwith forming a gap therebetween, each of the disk cutters beingconfigured by: alternately forming ridges which protrude in a ridge-likeshape toward an outer peripheral side, and valleys composed of acircumferential face or a flat face along a circumferential direction ona peripheral side face of a disk; and forming grooves which are openedin an outer peripheral end and in every other valley alternately formedin both faces of the disk, in peripheral edges of both the faces of thedisk, the disk cutter rolls being opposed to each other in a manner thatthe ridges of the disk cutters of one of the disk cutter rolls areplaced in the gaps of the disk cutters of another disk cutter roll,whereby slits each configured by a cut elongating in a longitudinaldirection are formed in the metal sheet, wherein

the valleys of the disk cutters of one of the disk cutter rolls whichare placed respectively on both sides of the metal sheet are arrangedwith being shifted in phase from the valleys of the disk cutters ofanother disk cutter roll.

According to the invention, since the valleys of the disk cutters areshifted in phase, one or more wires are pressed by the ridges to be bentin a ridge-like shape at the tip end of a drawn-out portion which ispressed by an end of the shifted valley to be drawn out in asubstantially straight manner from a node. In the wires which are bentvia the drawn-out portion, therefore, tensile stress produced during adeveloping process is dispersed, and hence the wire can be preventedfrom being easily corroded.

The invention provides a method of producing a grid for a battery platein which a metal sheet is passed between two rotating disk cutter rollsin each of which a plurality of disk cutters are placed on a same shaftwith forming a gap therebetween, each of the disk cutters beingconfigured by: alternately forming ridges which protrude in a ridge-likeshape toward an outer peripheral side, and valleys composed of acircumferential face or a flat face along a circumferential direction ona peripheral side face of a disk; and forming grooves which are openedin an outer peripheral end and in every other valley alternately formedin both faces of the disk, in peripheral edges of both the faces of thedisk, the disk cutter rolls being opposed to each other in a manner thatthe ridges of the disk cutters of one of the disk cutter rolls areplaced in the gaps of the disk cutters of another disk cutter roll,whereby slits each configured by a cut elongating in a longitudinaldirection are formed in the metal sheet, wherein

a length in a circumferential direction of the valleys of the diskcutters of the disk cutter roll which is placed on one side of the metalsheet is larger than a length of the valleys of the disk cutters of thedisk cutter roll which is placed on another side of the metal sheet.

According to the invention, since the valleys of the disk cutters aredifferent in length in the circumferential direction, one or more wiresare pressed by the ridges to be bent in a ridge-like shape at the tipend of a drawn-out portion which is pressed by an end of the longervalley to be drawn out in a substantially straight manner from a node.In the wires which are bent via the drawn-out portion, therefore,tensile stress produced during a developing process is dispersed, andhence the wires can be prevented from being easily corroded.

The invention provides a method of producing a grid for a battery platein which a metal sheet is passed between two rotating disk cutter rollsin each of which a plurality of disk cutters are placed on a same shaftwith forming a gap therebetween, each of the disk cutters beingconfigured by: alternately forming ridges which protrude in a ridge-likeshape toward an outer peripheral side, and valleys composed of acircumferential face or a flat face along a circumferential direction ona peripheral side face of a disk; and forming grooves which are openedin an outer peripheral end and in every other valley alternately formedin both faces of the disk, in peripheral edges of both the faces of thedisk, the disk cutter rolls being opposed to each other in a manner thatthe ridges of the disk cutters of one of the disk cutter rolls areplaced in the gaps of the disk cutters of another disk cutter roll,whereby slits each configured by a cut elongating in a longitudinaldirection are formed in the metal sheet, wherein

the grooves of the disk cutters of the disk cutter roll(s) which isplaced on one side or both sides of the metal sheet are opened only in apart of a whole circumferential length of the valleys.

According to the invention, since the grooves of the disk cutters areopened only in a part of the whole length of the valleys, the slits areformed also by the valleys other than the openings, and one or morewires are pressed by the ridges to be bent in a ridge-like shape at thetip end of a drawn-out portion which is drawn out in a substantiallystraight manner from a node. In the wires which are bent via thedrawn-out portion, therefore, tensile stress produced during adeveloping process is dispersed, and hence the wires can be preventedfrom being easily corroded.

The invention provides a method of producing a grid for a battery platein which a metal sheet is passed between two rotating disk cutter rollsin each of which a plurality of disk cutters are placed on a same shaftwith forming a gap therebetween, each of the disk cutters beingconfigured by: alternately forming ridges which protrude in a ridge-likeshape toward an outer peripheral side, and valleys composed of acircumferential face or a flat face along a circumferential direction ona peripheral side face of a disk; and forming grooves which are openedin an outer peripheral end and in every other valley alternately formedin both faces of the disk, in peripheral edges of both the faces of thedisk, the disk cutter rolls being opposed to each other in a manner thatthe ridges of the disk cutters of one of the disk cutter rolls areplaced in the gaps of the disk cutters of another disk cutter roll,whereby slits each configured by a cut elongating in a longitudinaldirection are formed in the metal sheet, wherein

two or more of settings are made, the settings including: setting inwhich the valleys of the disk cutters of one of the disk cutter rollswhich are placed on both sides of the metal sheet are arranged withbeing shifted in phase from the valleys of the disk cutters of anotherdisk cutter roll; setting in which a length in a circumferentialdirection of the valleys of the disk cutters of the disk cutter rollwhich is placed on the one side of the metal sheet is larger than alength of the valleys of the disk cutters of the disk cutter roll whichis placed on the other side of the metal sheet; and setting in which thegrooves of the disk cutters of the disk cutter roll(s) which is placedon the one side or both the sides of the metal sheet are opened only ina part of a whole circumferential length of the valleys.

According to the invention, two or more kinds of the settings in whichwires are pressed by protrusions to be bent in a ridge-like shape at thetip end of a drawn-out portion which is pressed by an end of thedrawn-out portion that is drawn out in a substantially straight mannerfrom a node are combinedly made. In the wires which are bent via thedrawn-out portion, therefore, tensile stress produced during adeveloping process is dispersed, and hence the wires can be preventedfrom being easily corroded.

Means for Solving Problem (2)

The invention provides a method of producing a grid for a battery platewherein slits in which a small bent portion is formed between a node anda fence-like portion are formed in a metal sheet by using disk cuttersof a rotary expander in each of which a plurality of ridges an apex ofwhich is shifted toward a front side in a rotational direction protrudewith forming a gap therebetween toward an outer circumference from adisk-like circumferential face at equal angular intervals, a small slopeis interposed between a valley constituting a peripheral side facebetween two of the ridges, and at least a front slope of a peripheralside face of a ridge which is rearward adjacent to the valley, therebyconnecting peripheral side faces, the small slope having an inclinationangle which is between angles of the two faces, and grooves which areformed at equal angular intervals in peripheral edges of both disk-likefaces are formed in every other gap face and opened alternately in boththe faces.

According to the invention, since, in the disk cutter of the rotaryexpander, a small slope is interposed between each of the valleys andthe slope of each of the ridges, the portion between the valley and theslope of the ridge is bent in two steps via the small slope, and thebending angles are gentle. When slits are formed in a metal sheet,therefore, the rising part of the fence-like portion between slits whichare pressed by ridges of the disk cutters 1 to protrude from a node in aridge-like shape is not bent by a steep angle, and can be bent in twosteps via the small slope, so that edges of meshes which are formed bydeveloping the slits are prevented from being easily corroded byelectrolyte. In the production method of the invention, particularly, atleast the bending angle which is formed by the valley and the slope ofthe ridge that is rearward adjacent thereto, and which is to beoriginally steep can be made gentle. Therefore, corrosion and a crack ofcorrosion in a node can be effectively prevented from occurring.

The invention provides a method of producing a grid for a battery platewherein slits in which a portion between a node and a fence-like portionis curved are formed in a metal sheet by using disk cutters of a rotaryexpander in each of which a plurality of ridges an apex of which isshifted toward a front side in a rotational direction protrude withforming a gap therebetween toward an outer circumference from adisk-like circumferential face at equal angular intervals, a curved faceis interposed between a valley constituting a peripheral side facebetween two of the ridges, and at least a front slope of a peripheralside face of a ridge which is rearward adjacent to the valley, therebyconnecting peripheral side faces, the curved face having a contact faceof an inclination angle which is between angles of the two faces, andgrooves which are formed at equal angular intervals in peripheral edgesof both disk-like faces are formed in every other gap face and openedalternately in both the faces.

According to the invention, since, in the disk cutter of the rotaryexpander, a curved face is interposed between each of the valleys andthe slope of each of the ridges, the portion between the valley and theslope of the ridge is smoothly bent via the curved face. When slits areformed in a metal sheet, therefore, the rising part of the fence-likeportion between slits which are pressed by ridges of the disk cutters 1to protrude from a node in a ridge-like shape is not angularly bent, andcan be bent smoothly in, for example, a rounded manner, so that edges ofmeshes which are formed by developing the slits are prevented from beingeasily corroded by electrolyte. In the production method of theinvention, particularly, at least the edge which is formed by the valleyand the slope of the ridge that is rearward adjacent thereto, and whichis to be originally steeply bent can be smoothed. Therefore, corrosionand a crack of corrosion in a node can be effectively prevented fromoccurring.

The invention provides a method of producing a grid for a battery platewherein slits in which a node is inclined are formed in a metal sheet byusing disk cutters of a rotary expander in each of which a plurality ofridges an apex of which is shifted toward a front side in a rotationaldirection protrude with forming a gap therebetween toward an outercircumference from a disk-like circumferential face at equal angularintervals, a valley constituting a peripheral side face between two ofthe ridges is formed into a face which is more inclined toward a centeras being more forward than a contact face contacting with acircumferential face in which all contacting faces contacting with thevalley have a same angular position at a center of a rotation shaft, andgrooves which are formed at equal angular intervals in peripheral edgesof both disk-like faces are formed in every other gap face and openedalternately in both the faces.

According to the invention, since the valley between the ridges of thedisk cutter used in the rotary expander is inclined toward the center asbeing more forward in the rotational direction, the bending angle formedby the valley and the steep slope of the ridge that is rearward adjacentthereto is made gentle, and that formed by the valley and the gentleslope of the ridge that is forward adjacent thereto is made steep.Consequently, the difference between the angles formed by the valleybetween the ridges and the slopes of the ridges that are respectivelyadjacent thereto on both the sides can be reduced. When slits are formedin a metal sheet, therefore, a node is inclined, and a phenomenon thatonly the rear side of the fence-like portion between slits is bent by asteep angle does not occur. As a result, the bending angles of the rearand front sides are averaged, whereby the edges can be prevented frombeing easily corroded by electrolyte. When the valley is configured byusing a face which is formed by inclining a circumferential face, theangle formed by contact faces of the circumferential face can be alwaysmade constant. Alternatively, the valley may be configured by aninclined flat face or another curved face.

The invention provides a method of producing a grid for a battery platein which a plate is produced by a rotary expander for forming slits in ametal sheet by using disk cutters in each of which a plurality of ridgesan apex of which is shifted toward a front side in a rotationaldirection protrude with forming a gap therebetween toward an outercircumference from a disk-like circumferential face at equal angularintervals, and grooves which are formed at equal angular intervals inperipheral edges of both disk-like faces are formed in every othervalley constituting a peripheral side face between the ridges, andopened alternately in both the faces, wherein

each of the valleys of the disk cutter is formed into a face which ismore inclined toward a center as being more forward than a contact facecontacting with a circumferential face in which all contacting facescontacting with the valley have a same angular position at a center of arotation shaft of the disk cutter.

According to the invention, since the valley between the ridges of thedisk cutter is inclined toward the center as being more forward in therotational direction, the bending angle formed by the valley and thesteep slope of the ridge that is rearward adjacent thereto is madegentle, and that formed by the valley and the gentle slope of the ridgethat is forward adjacent thereto is made steep. Consequently, thedifference between the angles formed by the valley between the ridgesand the slopes of the ridges that are respectively adjacent thereto onboth the sides can be reduced. Therefore, a phenomenon that only therear side of the fence-like portion between slits of the metal sheet isbent by a steep angle does not occur. As a result, the bending angles ofthe rear and front sides are averaged, whereby the edges can beprevented from being easily corroded by electrolyte. When the valley isconfigured by using a face which is formed by inclining acircumferential face, the angle formed by contact faces of thecircumferential face can be always made constant. Alternatively, thevalley may be configured by an inclined flat face or another curvedface.

The invention is characterized in that the valley is formed into a facewhich is more inclined by 1° or more toward the center as being moreforward than the contact face contacting with the circumferential facein which all contacting faces contacting with the valley have a sameangular position at the center of the rotation shaft of the disk cutter.

According to the invention, since the valley between the ridges of thedisk cutter has an inclination of 1° or more, the bending angle formedby the valley and the steep slope of the ridge that is rearward adjacentthereto can be surely made gentle.

The invention is characterized in that only a face of the valleyexcluding a front end portion is formed into a face which is moreinclined toward the center as being more forward than the contact facecontacting with the circumferential face in which all contacting facescontacting with the valley have a same angular position at the center ofthe rotation shaft of the disk cutter.

The valley between the ridges of the disk cutter may be configured by,for example, an inclined flat face in place of a face which is formed byinclining a circumferential face. When such a flat face has a smallinclination angle, there is a case where, in the vicinity of a portionwhere the flat face is adjacent to the front ridge, the contact face ofthe circumferential face is more inclined toward the center as beingmore forward. In some cases, the portion where the valley is adjacent tothe front ridge may be rounded, or a small slope having an intermediateinclination angle may be interposed between the valley and the frontridge. A contact face of the rounded face or the small slope may beinclined more outward than a contact face of a circumferential face atthe same angular position. According to the invention, however, thecontact face of the valley between the ridges of the disk cutterexcluding such a front end portion is more inclined toward the center asbeing more forward. Therefore, at least the bending angle formed by thevalley and the steep slope of the ridge that is rearward adjacentthereto can be surely made gentle. In some cases, also the portion wherethe valley is adjacent to the rear ridge may be rounded, or a smallslope having an intermediate inclination angle may be interposed betweenthe valley and the rear ridge. A contact face of the rounded face or thesmall slope is always more inclined toward the center than a contactface of a circumferential face at the same angular position.

The invention is characterized in that the circumferential face servingas a reference of inclination of the valley is a flat face connectingtogether cross lines between the circumferential face and the slopes ofthe ridges on both the sides.

A conventional valley is sometimes configured by a flat face in place ofa face extending along a circumferential face. In such a flat face, therear half is a face which is slightly inclined toward the center in alarger degree as being more forward than a contact face contacting witha circumferential face at the same angular position, but the front halfis a face which is slightly inclined toward the center in a largerdegree as being more rearward than a contact face contacting with acircumferential face at the same angular position. However, this canmake gentle the angle formed by the valley and the slope of the ridge,only by a small degree, and there is little difference between the casewhere the valley is configured by a flat face, and that where the valleyis configured by a face extending along a circumferential face. Bycontrast, according to the invention, the valley between the ridges ismore inclined than the flat face, and hence at least the bending angleformed by the valley and the steep slope of the ridge that is rearwardadjacent thereto can be surely made gentle.

Means for Solving Problem (3)

The invention provides a method of producing a grid for a battery platein which a rotary expander is used for forming a large number of zigzagslits in a metal sheet by passing the metal sheet between two or moreopposed disk cutter rolls, each of the disk cutter rolls beingconfigured by placing a plurality of disk cutters on a same shaft withforming a gap therebetween, each of the disk cutters being configuredby: alternately forming ridges in which a peripheral side face protrudesin a ridge-like shape toward an outer periphery from a referencecircumferential face of a predetermined radius, and valleys in which aperipheral side face composed of a face substantially extending alongthe reference circumferential face is formed, in a whole periphery of aperipheral edge of a disk, the reference circumferential face beingcentered at an axis of the disk; and, for each of the valleys, forming agroove which is opened in a peripheral side face of the valley, in aperipheral edge portion of one of disk faces in which valleys that areadjacent to each other via a ridge are formed in an oppositely reversemanner, wherein, in each of the disk cutters, an inclined face is formedin peripheral side faces which extend from apexes of ridges formed onboth sides of each of the valleys to the valley, the inclined face moreapproaching the axis as being nearer to the disk face in which thegroove of the valley is formed.

According to the invention, since the inclined face is formed in theperipheral side face of the ridge of the disk cutters, thin wires whichare configured between adjacent slits are formed in a ridge-like shapein a state where the wires are pretwisted along the inclined face whenslits are formed in a metal sheet by pressing of the ridge. Furthermore,the wires are inclined toward the groove. During the developing process,therefore, the node is pulled by the wires to be set to a directionwhich is opposite to the twisting direction. As a result, concentrationof torsion stress in the vicinity of the apexes of the wires during thedeveloping process can be reduced.

The inclined face which more approaches the axis as being nearer to thedisk face means that a contact face of the inclined face is inclined soas to more approach the axis of the disk cutter as being nearer to thedisk face, or means that the inclined face may have a part where acontact face is parallel to the axis but is not allowed to have a partwhere a contact face is inclined toward the outer peripheral side.

Preferably, the inclined face is formed from a position of a peripheralside face of a ridge, to a valley, the position being higher than thevalley by one third or more of a height in a radial direction of thedisk cutter extending from the valley to an apex of the ridge.Conventionally, torsion stress is concentrated on the vicinity of anapex of a wire. Therefore, it is preferable to form the inclined face ofa ridge of a disk cutter so as to extend as far as possible to thevicinity of the apex. When the inclined face is formed so as to extendfrom a level which is higher by one third or more of the ridge to thevalley, therefore, the twisting which is previously formed in the wirecan surely exert an effect.

Preferably, the inclination angle of the inclined face is equal to orsmaller than 40° with respect to the reference circumferential face.When the inclination angle of the inclined face is 40°, the angle of anedge between the inclined face and the disk face can be set to 60° ormore, and hence the metal sheet can be surely cut.

The grid for a battery plate of the invention is characterized in thatthe grid is produced by the production method for solving problem (3).

According to the invention, since concentration of torsion stress in thevicinity of the apexes of the wires during developing process can bereduced, a grid for a battery plate in which rupture or breakage hardlyoccurs is obtained.

Means for Solving Problem (4)

The invention provides a method of producing a grid for a battery platein which a plurality of parallel slits are cut in a metal sheet into azigzag pattern along an advancing direction of the metal sheet, wireswhich are formed by slits that are adjacent in a width direction of themetal sheet are elastically deformed in a ridge-like shape in both frontand ewe directions from a face of the metal sheet, flat regions whichare formed by non-slit portions are formed to become nodes of the wires,and the metal sheet is developed in the width direction, thereby formingmeshes, wherein the slits which are cut into a zigzag pattern are formedby passing the metal sheet through a roll pair in which rolls areopposed to each other, each of the rolls is configured by stacking diskcutters each having ridges and valleys, the ridges protruding at regularintervals from a circumference of the disk cutter, and, in the diskcutter, grooves are disposed in a thickness direction in each of thevalleys between the ridges and alternately in both disk facescorresponding to the nodes, and chamfered portions are disposed in anouter peripheral portion of a peripheral side face of the disk cutter,the outer peripheral portion excluding at least the ridges, thechamfered portions being lowered as being respectively nearer to thefaces in which the grooves are disposed.

The invention is characterized in that the chamfered portions betweenthe peripheral side face of the disk cutter and the disk faces of thedisk cutter in which the grooves are formed are planer or curvedchamfered portions.

The invention provides a battery comprising a grid for a battery platewhich is produced by the method for solving problem (4).

Means for Solving Problem (5)

The invention provides a method of producing a grid for a battery platein which a rotary expander is used for forming a large number of zigzagslits in a metal sheet by passing the metal sheet between two or moreopposed disk cutter rolls, each of the disk cutter rolls beingconfigured by placing a plurality of disk cutters on a same shaft withforming a gap therebetween, each of the disk cutters being configuredby: alternately forming ridges in which a peripheral side face protrudesin a ridge-like shape toward an outer periphery from a referencecircumferential face of a predetermined radius, and valleys in which aperipheral side face composed of a face substantially extending alongthe reference circumferential face is formed, in a whole periphery of aperipheral edge of a disk, the reference circumferential face beingcentered at a rotation axis of the disk; and, for each of the valleys,forming a groove which is opened in a peripheral side face of thevalley, in a peripheral edge portion of one of disk faces in whichvalleys that are adjacent to each other via a ridge are formed in anoppositely reverse manner, wherein, among the disk cutter rolls, a diskcutter roll which is opposed to a disk cutter roll having a disk cutterthat is disposed outermost is provided with a disk-like endmost diskcutter that is placed more outward than the outermost disk cutter, and aperipheral side face which is recessed toward a center with respect tothe reference circumferential face is formed in a valley (hereinafter,referred to as “endmost node forming valley”) which corresponds to avalley in a disk cutter of another disk cutter roll that is opposed viathe metal sheet, among valleys of the endmost disk cutter (in theendmost disk cutter, peripheral edge portions respectively correspondingto valleys of another disk cutter of a same disk cutter roll arereferred to as “valleys”), a groove being formed in a disk face in thegroove of the disk cutter of the other disk cutter roll, the disk facedirected to the endmost disk cutter.

In a usual node, deformation of a degree which is larger than thethickness of a metal sheet is produced because peripheral side faces ofvalleys of both disk cutters of disk cutter rolls which are opposed viathe metal sheet press the metal sheet from both the sides whileexceeding the cutting plane that is in the center between the axes ofthe disk cutter rolls. By contrast, according to the invention, theperipheral side faces of the endmost node forming valleys of the endmostdisk cutter are recessed with respect to the reference circumferentialface. Even when peripheral side faces of valleys of disk cutters of diskcutter rolls which are opposed via a metal sheet press an end portion ofthe endmost node while exceeding the cutting plane, therefore, theperipheral side faces of the endmost node forming valleys of the endmostdisk cutter press the basal portion of the endmost node with advancingin front of the cutting plane at the most. Consequently, deformation ofthe endmost node is reduced, so that wires drawn out from the node canbe surely prevented from being easily broken.

Preferably, the peripheral side face of the endmost node forming valleyis recessed toward the center with respect to a circumferential face ofa predetermined radius by a degree which is not smaller than 30% and notlarger than 70% of a thickness of the metal sheet. When the peripheralside face of the endmost node forming valley is recessed by 20% of thesheet thickness, for example, deformation of the endmost node exceeds80% of the sheet thickness, and is not largely different from that ofthe prior art. When the peripheral side face of the endmost node formingvalley is recessed by 80% of the sheet thickness, deformation of theendmost node can be restricted to a degree which slightly exceeds about20% of the sheet thickness. In the valleys of the endmost disk cutterother than the endmost node forming valleys, slits are formed bypressing a metal sheet while exceeding the cutting plane between thedisk cutter rolls, and, with respect to also the ridges (in the case ofthe endmost disk cutter, peripheral edge portions respectivelycorresponding to ridges of another disk cutter of the same disk cutterroll are referred to as “ridges”), pressing is usually conducted in asimilar manner. Therefore, a step corresponding to about 80% of thesheet thickness is produced between these portions and the endmost nodeforming valleys. By contrast, when the recess of the peripheral sideface of each of the endmost node forming valleys is set to about 50% ofthe sheet thickness, deformation of the endmost node and the stepbetween the node and the surrounding metal sheet can have an optimumsize of about 50% of the sheet thickness. Consequently, it is preferableto form a recess which is not smaller than 30% and not larger than 70%of the sheet thickness.

In the valleys of the endmost disk cutter, it is not always necessary toform a groove. In the valleys of the endmost disk cutter other than theendmost node forming valleys, the grooves are formed in the disk face ofthe endmost disk cutter which is outward directed. Therefore, it isentirely unnecessary to form such valleys, except the case where partsare shared by the endmost disk cutter and that which is placed in theopposite outer end. By contrast, the grooves of the endmost node formingvalleys of the endmost disk cutter are formed in the disk face of theendmost disk cutter which is inward directed, and a space for formingendmost nodes is required between the grooves, and those of valleys of adisk cutter which is opposed to the endmost disk cutter via the metalsheet. In a usual case, therefore, it is preferable to dispose groovesof the endmost node forming valleys. In the invention, the peripheralside faces of the endmost node forming valleys are recessed. When therecesses are formed to be sufficiently large, therefore, an enough spacecan be ensured between the valleys and the grooves of the valleys of theopposed disk cutter, and hence forcible deformation is not produced inthe endmost nodes, with the result that formation of grooves is notalways necessary.

Preferably, an inclined face which more approaches a center as beingnearer to an outer side is formed in each of peripheral side faces ofthe valleys and/or the ridges of the endmost disk cutter other than theendmost node forming valleys. In the valleys of the endmost disk cutterother than the endmost node forming valleys, slits are formed bypressing the metal sheet while exceeding the cutting plane between thedisk cutter rolls. Also in the ridges, usually, pressing is conducted ina similar manner. Therefore, a step is produced between these portionsand the endmost node forming valleys in which the peripheral side faceis recessed, so that step-like undulation may be formed in the frameportion of the metal sheet. When each of the peripheral side faces ofthe valleys and the ridges other than the endmost node forming valleysis formed as an inclined face, the frame portion of the metal sheet canbe gently bent.

In each of the ridges of the endmost disk cutter, preferably, aperipheral side face of the reference circumferential face or aperipheral side face which is nearer to the center than the referencecircumferential face is formed. When the peripheral side faces of theridges of the endmost disk cutter protrude in a ridge-like shape in thesame manner as those of a usual disk cutter, the edge of the frameportion of the metal sheet is unnecessarily vertically pressed to causedeformation, because no slits are formed outside the ridges. Since theridge-like protruding peripheral side face of each of the ridges of ausual disk cutter presses the metal sheet while greatly exceeding thecutting plane between the disk cutter rolls, the metal sheet can be cutin many cases, even when the peripheral side face of each of the valleysof the endmost disk cutter which is opposed to the usual disk cutterdoes not exceed the cutting plane. Therefore, the peripheral side faceof each of the valleys of the endmost disk cutter can be formed in thereference circumferential face. When a peripheral side face which isnearer to the center at a degree similar to the peripheral side faces ofthe endmost node forming valleys is formed, for example, the frameportion of the metal sheet can be prevented from largely undulating.

The method of producing a grid for a battery plate according to theinvention is characterized in that an inclined face is formed in theperipheral side face of the endmost node forming valley, the inclinedface being nearer to the center as being more inward.

In the case where a groove is not formed in the endmost node formingvalley, when the peripheral side face is recessed by a small degree fromthe reference circumferential face, the endmost node is deformed only bymeans of the space in the recess of the valley of the disk cutter whichis opposed via the metal sheet, and hence there is the possibility that,when the amount of deformation is large, the endmost node is deformed inan extremely abrupt manner. According to the invention, an inclined faceis formed in the peripheral side face of the endmost node formingvalley, and hence the endmost node can be gently deformed along theinclined face. Even in the case where a groove is formed in the endmostnode forming valley, the deformation of the endmost node can be mademore gentle by the formation of an inclined face in the peripheral sideface.

The grid for a battery plate of the invention is characterized in thatthe grid is produced by the production method for solving problem (5).

According to the invention, a grid for a battery plate in which wiresdrawn out from the endmost nodes are hardly broken is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial enlarged perspective view showing a first example ofa first embodiment of the invention, and showing the vicinity of a nodeof a grid in an enlarged manner;

FIG. 2 is a partial enlarged schematic view showing the first example ofthe first embodiment of the invention, and schematically showing in anenlarged manner a portion where disk cutters which are vertically placedoverlap with each other;

FIG. 3 is a partial enlarged schematic view showing a second example ofthe first embodiment of the invention, and schematically showing in anenlarged manner a portion where disk cutters which are vertically placedoverlap with each other;

FIG. 4 is a partial enlarged perspective view showing the second exampleof the first embodiment of the invention, and showing in an enlargedmanner the vicinity of a node of a grid;

FIG. 5 is a partial enlarged schematic view showing a third example ofthe first embodiment of the invention, and schematically showing in anenlarged manner a portion where upper and lower phase-shifted diskcutters overlap with each other;

FIG. 6 is a partial enlarged perspective view showing the third exampleof the first embodiment of the invention, and showing in an enlargedmanner the vicinity of a node of a grid which is produced by thephase-shifted disk cutters;

FIG. 7 is a partial enlarged schematic view showing a fourth example ofthe first embodiment of the invention, and schematically showing in anenlarged manner a portion where disk cutters which are vertically placedoverlap with each other;

FIG. 8 is a partial enlarged perspective view showing the fourth exampleof the first embodiment of the invention, and showing in an enlargedmanner the vicinity of a node of a grid;

FIG. 9 is a partial enlarged schematic view showing a fifth example ofthe first embodiment of the invention, and schematically showing in anenlarged manner a portion where disk cutters which are vertically placedwith shifting grooves to one side overlap with each other;

FIG. 10 is a partial enlarged perspective view showing the fifth exampleof the first embodiment of the invention, and showing in an enlargedmanner the vicinity of a node of a grid which is produced by the diskcutters having grooves shifted to one side;

FIG. 11 is a partial enlarged schematic view showing a sixth example ofthe first embodiment of the invention, and schematically showing in anenlarged manner a portion where disk cutters which are vertically placedwith shifting grooves in opposite directions overlap with each other;

FIG. 12 is a partial enlarged perspective view showing the sixth exampleof the first embodiment of the invention, and showing in an enlargedmanner the vicinity of a node of a grid which is produced by the diskcutters having grooves shifted in opposite directions;

FIG. 13 is a partial enlarged schematic view showing a seventh exampleof the first embodiment of the invention, and schematically showing inan enlarged manner a portion where upper and lower phase-shifted diskcutters overlap with each other;

FIG. 14 is a partial enlarged perspective view showing the seventhexample of the first embodiment of the invention, and showing in anenlarged manner the vicinity of a node of a grid which is produced bythe phase-shifted disk cutters;

FIG. 15 is a partial enlarged front view showing a second embodiment ofthe invention, and showing a valley of a disk cutter;

FIG. 16 is a partial enlarged front longitudinal section view showingthe second embodiment of the invention, and showing a fence-like portionbetween slits protruding in a ridge-like shape in a metal sheet;

FIG. 17 is a partial enlarged front view showing an embodiment of theinvention, and showing a case where, in place of a small slope, a curvedfaces is interposed in both sides of a gap face of a disk cutter;

FIG. 18 is a partial enlarged front view showing a third embodiment ofthe invention, and showing an inclined valley of a disk cutter;

FIG. 19 is a partial enlarged front longitudinal section view showingthe third embodiment of the invention, and showing a fence-like portionbetween slits protruding in a ridge-like shape in a metal sheet;

FIG. 20 is a front view showing a fourth embodiment of the invention,and showing the whole of a disk cutter, and a peripheral edge of thedisk cutter in an enlarged manner;

FIG. 21 is a partial enlarged perspective view showing the fourthembodiment of the invention, and showing inclined faces formed inperipheral side faces of ridges which are opposed across a valley of thedisk cutter;

FIG. 22 is a partial enlarged side longitudinal section view showing thefourth embodiment of the invention, and showing a slit forming step of arotary expander and illustrating a manner in which wires of a metalsheet are twisted with being pressed by the inclined faces formed inridges of disk cutters of upper and lower disk cutter rolls;

FIG. 23 is a partial enlarged perspective view showing the fourthembodiment of the invention, and showing a lead sheet and illustrating anode formed in the slit forming step, and four wires connected thereto;

FIG. 24 is a partial enlarged perspective view showing the fourthembodiment of the invention, and showing another first configurationexample of the inclined faces formed in peripheral side faces of ridgeswhich are opposed across a valley of the disk cutter;

FIG. 25 is a partial enlarged perspective view showing the fourthembodiment of the invention, and showing another second configurationexample of the inclined faces formed in peripheral side faces of ridgeswhich are opposed across a valley of the disk cutter;

FIG. 26 is a partial enlarged perspective view showing the fourthembodiment of the invention, and showing another third configurationexample of the inclined faces formed in peripheral side faces of ridgeswhich are opposed across a valley of the disk cutter;

FIG. 27( a) is a schematic view showing a first example of a fifthembodiment of the invention, and showing a section shape taken along aplane passing through the disk center of a disk cutter and perpendicularto a disk face in the case where a node is formed in a metal sheet by acutting tool, and FIG. 27( b) is a partial perspective view showing thevicinity of a valley of the disk cutter of the fifth embodiment;

FIG. 28( a) is a schematic view showing a second example of the fifthembodiment of the invention, and showing a section shape taken along aplane passing through the disk center of a disk cutter and perpendicularto a disk face in the case where a node is formed in a metal sheet by acutting tool, and FIG. 28( b) is a partial perspective view showing thevicinity of a valley of the disk cutter of the fifth embodiment;

FIG. 29( a) is a schematic view showing a third example of the fifthembodiment of the invention, and showing a section shape taken along aplane passing through the disk center of a disk cutter and perpendicularto a disk face in the case where a node is formed in a metal sheet by acutting tool, and FIG. 29( b) is a partial perspective view showing thevicinity of a valley of the disk cutter of the fifth embodiment;

FIG. 30 is a partial enlarged front longitudinal section view showing asixth embodiment of the invention, and showing a process of formingslits in a metal sheet by disk cutters of upper and lower disk cutterrolls;

FIG. 31 is a side view showing the sixth embodiment of the invention,and showing the configuration of an endmost disk cutter;

FIG. 32 is a partial enlarged perspective view showing the sixthembodiment of the invention, and showing the configuration of theendmost disk cutter;

FIG. 33 is a partial enlarged perspective view showing the sixthembodiment of the invention, and showing the vicinity of an endmost nodein a grid which is obtained by developing slits formed in a metal sheet;

FIG. 34 is a partial enlarged front longitudinal section view showingthe sixth embodiment of the invention, and showing a process of formingslits in a metal sheet by using an endmost disk cutter in which inclinedfaces are formed in peripheral side faces of ridges;

FIG. 35 is a partial enlarged front longitudinal section view showingthe sixth embodiment of the invention, and showing a process of formingslits in a metal sheet by using an endmost disk cutter in whichperipheral side faces of valleys are configured as a circumferentialface;

FIG. 36 is a partial enlarged front longitudinal section view showingthe sixth embodiment of the invention, and showing a process of formingslits in a metal sheet by using an endmost disk cutter in whichperipheral side faces of valleys are recessed;

FIG. 37 is a front view showing a prior art example, and showing theconfiguration of a disk cutter and a peripheral edge of the disk cutter;

FIG. 38 is a front view showing a prior art example, and showing a stepof forming slits in a metal sheet by a disk cutter in a rotary expander;

FIG. 39 is a partial enlarged side longitudinal section view showing aprior art example, and showing an arrangement of disk cutters in arotary expander;

FIG. 40 is a partial enlarged perspective view showing a prior artexample, and showing a grid which is obtained by forming slits in ametal sheet and developing the slits;

FIG. 41 is a partial enlarged view showing a prior art example, andshowing ridges and valleys of a disk cutter;

FIG. 42 is a partial enlarged side longitudinal section view showing aprior art example, and showing a fence-like portion between slitsprotruding in a ridge-like shape in a metal sheet;

FIG. 43 is a partial enlarged plan view showing a prior art example, andshowing a grid which is formed by developing slits of a metal sheet intomeshes;

FIG. 44 is a partial enlarged perspective view showing a prior artexample, and showing a metal sheet illustrating a node formed in theslit forming step, and wires connected thereto;

FIG. 45 is a partial enlarged perspective view showing a prior artexample, and showing a grid which is obtained by, in a developing step,developing a metal sheet in which slits are formed in a slit formingstep;

FIG. 46( a) is a schematic view showing a prior art example, and showinga section shape taken along a plane passing through the disk center of adisk cutter and perpendicular to a disk face in the case where a node isformed in a metal sheet by a cutting tool, and FIG. 46( b) is a partialsection view showing the node formed by the cutter;

FIG. 47 is a partial enlarged front longitudinal section view showing aprior art example, and showing a process of forming slits in a metalsheet by disk cutters of upper and lower disk cutter rolls;

FIG. 48 is a side view showing a prior art example, and showing theconfiguration of an endmost disk cutter;

FIG. 49 is a partial enlarged perspective view showing a prior artexample, and showing the configuration of the endmost disk cutter; and

FIG. 50 is a partial enlarged perspective view showing a prior artexample, and showing the vicinity of an endmost node in a grid which isobtained by developing slits formed in a metal sheet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the invention will be described withreference to the accompanying drawings.

Embodiment (1) of the Invention

FIGS. 1 and 2 show a first example of a first embodiment of theinvention. FIG. 1 is a partial enlarged perspective view showing thevicinity of a node of a grid in an enlarged manner, and FIG. 2 is apartial enlarged schematic view schematically showing in an enlargedmanner a portion where disk cutters which are vertically placed overlapwith each other. The components having the same functions as those ofthe prior art example shown in FIGS. 37 to 50 are denoted by theidentical reference numerals.

In the same manner as the prior art example, in the embodiment, a gridwhich is to be used in a battery plate of a lead storage battery will bedescribed, and also a method of producing the grid for a battery platefrom the metal sheet 2 by a rotary expander will be described.

The embodiment is a case where, as shown in FIG. 2, the disk cutters 1,1 which are vertically opposed to each other are changed in phase. Aplurality of the upper and lower disk cutters 1, 1 are combined so as tobe used as disk cutter rolls, respectively. In the disk cutters 1, 1,lengths in the circumferential direction of the valleys 1 b and theridges 1 a are equal to each other. Conventionally, such disk cutters 1,1 are placed and rotated while their phases coincide with each other sothat the valleys 1 b, 1 b vertically overlap with each other withoutbeing mutually shifted. By contrast, in the embodiment, the phase of thedisk cutter 1 which is placed in the upper side leads by a phase angleα. In the embodiment, namely, the upper disk cutter 1 is placed withbeing slightly shifted toward the front side in the rotational direction(indicated by the arrow in FIG. 2). In order to facilitate theunderstanding of the phase shifting, the upper and lower disk cutters 1,1 in FIG. 2 are shown with being vertically separated from each other.In practice, the disk cutters are placed so closely that the valleys 1 bslightly overlap with each other. In FIG. 2, the circumferential facesof the disk cutters 1, 1 are shown with being developed to a horizontalplane.

When the metal sheet 2 is passed between the upper and lower diskcutters 1, 1 in the prior art which are not shifted in phase, the slits2 a are formed by the overlapping portions between the upper and lowerridges 1 a, 1 a, and those between the upper and lower valleys 1 b, 1 bwhere the grooves 1 c, 1 c are opened with facing in oppositedirections, and the nodes 2 c are formed by the overlapping portionsbetween the upper and lower valleys 1 b where the grooves 1 c are openedwith facing each other. The length of each node 2 c in the longitudinaldirection (the advancing direction indicated by the arrow in FIG. 2) isequal to the length in the circumferential direction of each valley 1 b,i.e., the width of each groove 1 c.

By contrast, when the metal sheet 2 is passed between the disk cutters1, 1 in the embodiment, the nodes 2 c are formed only by the portionswhere the upper and lower grooves 1 c, 1 c overlap with each other,because the openings of the grooves are shifted from each other, withthe result that the length of the nodes 2 in the longitudinal directionis shorter than the length of the valleys 1 b and the width of thegrooves 1 c. As shown in FIG. 1, in the rear side of each node 2 c inthe longitudinal direction of the metal sheet 2, the wire 2 b (the leftfront one in the figure) which is downward pressed by the ridge 1 a ofthe upper disk cutter 1 that leads in phase is downward bent withstarting immediately from the basal end of the node 2 c, and the wire 2b (the left rear one in the figure) which is upward pressed by the ridge1 a of the lower disk cutter 1 that lags in phase is upward bent at thetip end of a drawn-out portion 2 d which is rearward drawn out from thenode 2 c in the longitudinal direction of the metal sheet 2. In thefront side of the node 2 c in the longitudinal direction of the metalsheet 2, the wire 2 b (the right rear one in the figure) which is upwardpressed by the ridge 1 a of the lower disk cutter 1 that lags in phaseis upward bent with starting immediately from the basal end of the node2 c, and the wire 2 b (the right front one in the figure) which isdownward pressed by the ridge 1 a of the upper disk cutter 1 that leadsin phase is downward bent at the tip end of a drawn-out portion 2 dwhich is forward drawn out from the node 2 c in the longitudinaldirection of the metal sheet 2. The drawn-out portions 2 d are portionswhich fail to be completely formed as the node 2 c, because they arecaused to remain flat by the valley 1 b of one of the disk cutters 1 inthe same manner as the node 2 c, but the metal sheet 2 is pressed to becut by the ridge 1 a of the other disk cutter 1 where no groove 1 cexists.

As a result, in the grid of the embodiment, among the four wires 2 bconnected to the node 2 c, the two diagonal wires 2 b (the left frontand right rear ones in the figure) are bent with starting immediatelyfrom the basal end of the node 2 c and diagonally elongate in the samemanner as in the prior art example, but the remaining two wires 2 b (theleft rear and right front ones in the figure) are bent at the tip endsof the drawn-out portions 2 d which are once drawn out from the basalend of the node 2 c in the longitudinal direction of the metal sheet 2,and then diagonally elongate. When the grid is stretched in the widthdirection of the metal sheet 2 to be developed, therefore, the tensilestress applied to the two wires 2 b which are drawn out and bent fromthe node 2 c via the drawn-out portions 2 d is dispersed to the wholedrawn-out portions 2 d, so that, even after the developing process, thedrawn-out portions 2 d can maintain the state where the portions aredrawn out in a substantially longitudinal direction. FIG. 1 shows thegrid after development. In practice, also in the grid which isimmediately after the formation of the slits 2 a by the disk cutters 1,1, the drawing out angles of the wires are made gentle, and there is nodifference in the drawn-out portions 2 d before and after development.With respect to the two wires 2 b in which no drawn-out portion 2 d isdisposed, therefore, the tensile stress during the developing process isconcentrated in the basal end of the node 2 c, and hence there is thepossibility that large distortion or rupture occurs. In the same manneras the prior art example, consequently, the wires are easily corroded byelectrolyte during use of the storage battery. By contrast, in the twowires 2 b in which the drawn-out portion 2 d is disposed, largedistortion or rupture does not occur, so that corrosion due toelectrolyte hardly occurs. As a result, the possibility that a crack ofsuch corrosion occurs in the wires 2 b can be reduced.

The embodiment can be implemented simply by using as they are the diskcutters 1 which are shown in the prior art example, and shifting thephases of the upper and lower disk cutters when the disk cutter rollsare to be disposed.

FIGS. 3 and 4 show a second example of the first embodiment of theinvention. FIG. 3 is a partial enlarged schematic view schematicallyshowing a portion where disk cutters which are vertically placed overlapwith each other, and FIG. 4 is a partial enlarged perspective viewshowing the vicinity of a node of a grid in an enlarged manner.

FIGS. 5 and 6 show a third example of the first embodiment of theinvention. FIG. 5 is a partial enlarged schematic view schematicallyshowing in an enlarged manner a portion where upper and lowerphase-shifted disk cutters overlap with each other, and FIG. 6 is apartial enlarged perspective view showing in an enlarged manner thevicinity of a node of a grid which is produced by the phase-shifted diskcutters. The components having the same functions as those of the firstembodiment shown in FIGS. 1 and 2 are denoted by the identical referencenumerals. In the same manner as FIG. 2, FIGS. 3 and 5 show the upper andlower disk cutters with being vertically separated from each other, andthe circumferential faces are shown with being developed to a horizontalplane. In the same manner as FIG. 1, actually, FIGS. 4 and 6 show a gridwhich has been developed.

In the same manner as the first example, also in the second and thirdexamples of the embodiment, a grid for a plate of a storage battery willbe described, and also a method of producing the grid from the metalsheet 2 by the upper and lower disk cutters 1, 1 of the rotary expanderwill be described. In the embodiment, as shown in FIG. 3, the lengths ofthe valleys 1 b of the disk cutters 1, 1 which are vertically opposed toeach other are different. In the embodiment, namely, the length Ld inthe circumferential direction of the valley 1 b of the disk cutter 1which is placed in the lower side is longer than the length Lu of thevalley 1 b of the disk cutter 1 which is placed in the upper side. Inaccordance with the above, the width of the groove 1 c by which thegroove is opened in each of the valleys 1 b of the lower disk cutter 1is longer. In the lower disk cutter 1, the pitch of the valleys 1 balong the circumference is made equal to that of the upper disk cutter1, by reducing the length of the ridges 1 a in the circumferentialdirection. Moreover, the phases of the upper and lower disk cutters 1coincide with each other, so that each of the valleys 1 b of the upperdisk cutter 1 overlaps just with the center of the whole length of thecorresponding valley 1 b of the lower disk cutter 1.

When the metal sheet 2 is passed between the upper and lower diskcutters 1, 1, only the nodes 2 c the length of which is equal to theshorter width of the grooves 1 c of the upper disk cutter 1 are formedin the grid, because the widths of the upper and lower grooves 1 c, 1 care different from each other. As shown in FIG. 4, in one side of eachnode 2 c in the width direction of the metal sheet 2, two wires (thefront ones in the figure) which are downward pressed by the ridge 1 a ofthe upper disk cutter 1 having the shorter valleys 1 b are downward bentwith starting immediately from the basal end of the node 2 c, and bycontrast two wires (the rear ones in the figure) which are upwardpressed by the ridge 1 a of the lower disk cutter 1 having the longervalleys 1 b are upward bent at the tip ends of the drawn-out portions 2d which are frontward and backward drawn out from the node 2 c in thelongitudinal direction of the metal sheet 2.

When the grid is stretched in the width direction of the metal sheet 2to be developed, the tensile stress applied to the two wires 2 b whichare drawn out and bent from the node 2 c via the drawn-out portions 2 dis dispersed to the whole drawn-out portions 2 d, so that, even afterthe developing process, the drawn-out portions 2 d can maintain thestate where the portions are drawn out in a substantially longitudinaldirection. In the two wires 2 b which are bent at the tip ends of thedrawn-out portions 2 d, therefore, large distortion or rupture does notoccur during the developing process, so that corrosion due toelectrolyte hardly occurs. As a result, the possibility that a crack ofcorrosion occurs in the wires 2 b during use of the storage battery canbe reduced.

In the second example, the case where the phases of the upper and lowerdisk cutters 1, 1 coincide with each other has been described.Alternatively, the phases may be shifted from each other. As shown inFIG. 5, for example, the lower disk cutter 1 may lead in phase so thatthe rear ends of the grooves 1 c, 1 c vertically coincide with eachother. As a result, as shown in FIG. 6, the wire 2 b (the right rearfront one in the figure) which is upward pressed by the ridge 1 a of thelower disk cutter 1 having the longer valleys 1 b is upward bent at thetip end of the drawn-out portion 2 d which is forward drawn out from thenode 2 c in the longitudinal direction. The tensile stress applied tothe wire 2 b during the developing process is dispersed to the wholedrawn-out portion 2 d, whereby, although for one bar for each of thenodes 2 c, the possibility that a crack of corrosion due to electrolyteoccurs in the wire 2 b during use of the storage battery can be reduced.

FIGS. 7 and 8 show a fourth example of the first embodiment of theinvention. FIG. 7 is a partial enlarged schematic view schematicallyshowing in an enlarged manner a portion where disk cutters which arevertically placed overlap with each other, and FIG. 8 is a partialenlarged perspective view showing in an enlarged manner the vicinity ofa node of a grid. FIGS. 9 and 10 show a fifth example of the firstembodiment of the invention. FIG. 9 is a partial enlarged schematic viewschematically showing in an enlarged manner a portion where disk cutterswhich are vertically placed with shifting grooves to one side overlapwith each other, and FIG. 10 is a partial enlarged perspective viewshowing in an enlarged manner the vicinity of a node of a grid which isproduced by the disk cutters having grooves shifted to one side.

FIGS. 11 and 12 show a sixth example of the first embodiment of theinvention. FIG. 11 is a partial enlarged schematic view schematicallyshowing in an enlarged manner a portion where disk cutters which arevertically placed with shifting grooves in opposite directions overlapwith each other, and FIG. 12 is a partial enlarged perspective viewshowing in an enlarged manner the vicinity of a node of a grid which isproduced by the disk cutters having grooves shifted in oppositedirections.

FIGS. 13 and 14 show a seventh example of the first embodiment of theinvention. FIG. 13 is a partial enlarged schematic view schematicallyshowing in an enlarged manner a portion where upper and lowerphase-shifted disk cutters overlap with each other, and FIG. 14 is apartial enlarged perspective view showing in an enlarged manner thevicinity of a node of a grid which is produced by the phase-shifted diskcutters.

The components having the same functions as those of the examples shownin FIGS. 1 and 6 are denoted by the identical reference numerals. In thesame manner as FIG. 2 and the like, FIGS. 7, 9, 11, and 13 show theupper and lower disk cutters with being vertically separated from eachother, and the circumferential faces are shown with being developed to ahorizontal plane. In the same manner as FIG. 1 and the like, actually,FIGS. 8, 10, 12, and 14 show a grid which has been developed.

In the same manner as the first to third examples, also in the examples(FIGS. 7 to 14) of the embodiment, a grid for a plate of a storagebattery will be described, and also a method of producing the grid fromthe lead sheet 2 by the upper and lower disk cutters 1, 1 of the rotaryexpander will be described. In the fourth example of the embodiment, asshown in FIG. 7, the length Lw of the valleys 1 b is longer than thewidth Ln of the grooves 1 c. In FIG. 7, particularly, the disk cutter 1is used in which each of the grooves 1 c is opened at the width Ln andonly in the center area of the whole length Lw of a flat face 1 b(Ln<Lw). In FIG. 7, the phases of the upper and lower disk cutters 1, 1coincide with each other.

When the metal sheet 2 is passed between the upper and lower diskcutters 1, 1, the node 2 c the length of which is equal to the width Lnof the grooves 1 c is formed, because the upper and lower grooves 1 c, 1c coincide and overlap with each other. In the four wires 2 b connectedto the node 2 c, their ends are pressed by the valley 1 b where thegroove 1 c is not opened. As shown in FIG. 8, therefore, the wires areupward or downward bent at the tip ends of the drawn-out portions 2 dwhich are frontward and backward drawn out from the node 2 c in thelongitudinal direction of the lead sheet 2.

When the grid is stretched in the width direction of the metal sheet 2to be developed, the tensile stress applied to the four wires 2 b whichare drawn out and bent from the node 2 c via the drawn-out portions 2 dis dispersed to the whole drawn-out portions 2 d, so that, even afterthe developing process, the drawn-out portions 2 d can maintain thestate where the portions are drawn out in a substantially longitudinaldirection. In all the basal ends where the four wires 2 b are connectedto the node 2, therefore, large distortion or rupture does not occurduring the developing process, so that corrosion due to electrolytehardly occurs. As a result, the possibility that a crack of corrosionoccurs in the wires 2 b during use of the storage battery can beremarkably reduced.

In the fourth example of the embodiment, the case where the groove 1 cis opened in the center of the valley 1 b has been described. In thefifth example, the groove 1 c is opened with being shifted to one end ofthe valley 1 b as shown in FIG. 9. In this case also, the upper andlower grooves 1 c, 1 c coincide and overlap with each other, and hencethe node 20 the length of which is equal to the width Ln of the grooves1 c is formed. As shown in FIG. 10, however, in one side of each node 2c in the width direction of the metal sheet 2, two wires 2 b (the rightones in the figure) which are vertically pressed by the ridges 1 a whichprotrude immediately from the ends of the valleys 1 b where the groove 1c is opened are vertically bent with starting immediately from the basalend of the node 2 c, and by contrast two wires (the left ones in thefigure) which are vertically pressed by the ends of the valleys 1 bwhere the groove 1 c is not opened are vertically bent at the tip endsof the drawn-out portions 2 d which are rearward drawn out from the node2 c in the longitudinal direction of the metal sheet 2. The tensilestress applied to the two wires 2 b during the developing process isdispersed to the whole drawn-out portions 2 d, whereby the possibilitythat a crack of corrosion due to electrolyte occurs in the wires 2 bduring use of the storage battery can be reduced.

As shown in FIG. 11, the grooves 10 which are opened with being shiftedto ends of the valleys 1 b may be formed respectively in the ends whichare on the opposite sides along the frontward and backward directions inthe upper and lower disk cutters 1. The upper and lower disk cutters 1are oppositely rotated. In the case of the disk cutters 1 shown in FIG.9, therefore, disk cutters having different shapes are used as the upperand lower disk cutters. By contrast, in the case of FIG. 11, diskcutters having the same shape can be used as the upper and lower diskcutters, and hence sharing of the parts can be attained. In this case,the upper and lower grooves 1 c, 1 c are shifted from each other, andhence the node 2 c is formed only by the portion where the groovesoverlap with each other. As shown in FIG. 12, all of the four wires 2 bconnected to the node 2 c are vertically pressed by the valleys 1 bwhere the groove 1 c is opened, and the valleys 1 b where the groove 1 cis not opened, and hence vertically bent at the tip ends of thedrawn-out portions 2 d which are frontward and backward drawn out fromthe node 2 c in the longitudinal direction of the metal sheet 2. Thetensile stress applied to the four wires 2 b during the developingprocess is dispersed to the whole drawn-out portions 2 d, whereby thepossibility that a crack of corrosion due to electrolyte occurs in thewires 2 b during use of the storage battery can be remarkably reduced.

As shown in FIG. 13, the grooves 1 c which are opened with being shiftedto ends of the valleys 1 b may be formed respectively in the ends whichare on the opposite sides along the frontward and backward directions inthe upper and lower disk cutters 1, and may be shifted in phase so thatthe upper and lower grooves 1 c, 1 c coincide and overlap with eachother. In this case also, the upper and lower valleys 1 b, 1 b areshifted from each other, but the upper and lower grooves 1 c, 1 ccoincide and overlap with each other, so that the node 2 c the length ofwhich is equal to the width Ln of the grooves 1 c is formed. As shown inFIG. 14, among the four wires 2 b connected to the node 2 c, the twodiagonal wires 2 b (the left rear and right front ones in the figure)are pressed by the upper and lower protrusions 1 a to be vertically bentwith starting immediately from the basal end of the node 2 c, but theremaining two wires 2 b (the left front and right rear ones in thefigure) which are vertically pressed by the ends of the valleys 1 bwhere the groove is not opened are vertically bent at the tip ends ofthe drawn-out portions 2 d which are drawn out from the basal end of thenode 2 c in the longitudinal direction of the metal sheet 2. The tensilestress applied to the two wires 2 b during the developing process isdispersed to the whole drawn-out portions 2 d, whereby the possibilitythat a crack of corrosion due to electrolyte occurs in the wires 2 bduring use of the storage battery can be reduced.

In the first to sixth examples, the various combinations in which thephases of the upper and lower disk cutters 1, 1 are shifted from eachother, the upper and lower flat faces 1 b, 1 b have different lengths,or the length of the valleys 1 b of the disk cutters 1 is longer thanthe width of the grooves 1 c have been described. Any other combinationsof the disk cutters 1, 1 can be used as far as at least one of the wires2 b connected to the node 2 c has a shape in which it is bent via thedrawn-out portion 2 d. For example, the upper and lower valleys 1 b, 1 bmay have different lengths, and the width of both or one of the upperand lower grooves 1 c may be shorter than the lengths of the valleys 1b. In addition to this, the phases of the upper and lower disk cutters1, 1 may be shifted from each other.

In the first to sixth examples, in order to simplify the description,the case where the grid is produced by passing the metal sheet 2 of leador a lead alloy between the upper and lower disk cutters 1, 1 has beendescribed. The manner of arranging disk cutter rolls in which such diskcutters 1 are combinedly used can be arbitrarily selected, and is notrestricted to the case where the metal sheet 2 is passed through twoopposed disk cutter rolls. The grid may be produced with arranging threeor more disk cutter rolls in the transportation path of the metal sheet2.

In the first to sixth examples, the case where the metal sheet 2 of leador a lead alloy is processed to produce a grid for a battery plate hasbeen described. The invention can be similarly applied also to the casewhere the metal sheet 2 of a metal other than lead or a lead alloy isprocessed to produce another grid for a battery plate.

As apparent from the above description, according to the grid for abattery plate of the invention, a wire is bent at the tip end of adrawn-out portion which is drawn out in a substantially straight mannerfrom a node, and hence the wire can be prevented from being easilycorroded to cause a crack of corrosion.

According to the method of producing a grid for a battery plate of theinvention, a wire is bent at the tip end of a drawn-out portion which isdrawn out in a substantially straight manner from a node, whereby wiresof a produced grid can be prevented from being easily corroded.

Embodiment (2) of the Invention

Next, a second embodiment of the invention will be described withreference to the accompanying drawings.

FIGS. 15 to 17 show the second embodiment of the invention. FIG. 15 is apartial enlarged front view showing a gap face of a disk cutter, FIG. 16is a partial enlarged front longitudinal section view showing afence-like portion between slits protruding in a ridge-like shape in ametal sheet, and FIG. 17 is a partial enlarged front view showing a casewhere, in place of a small slope, a curved faces is interposed in bothsides of a valley of a disk cutter.

In a manner similar to the prior art example shown in FIGS. 37 to 50,also the embodiment of the invention relates to the disk cutter 1 of arotary expander. The disk cutter 1 is a cutting tool in which a largenumber of ridges 1 a protrude from the peripheral side face of a thindisk-like steel plate. The ridges 1 a protrude at equal angularintervals from the peripheral side face of the disk cutter 1, and arearranged with forming a constant gap between adjacent ridges. In thesame manner as in the prior art example shown in FIG. 41, each of theridges 1 a is formed so as to protrude in a ridge-like shape from thecircumferential face A, and the apex 1 i (see FIG. 41) of the ridge 1 ais rounded so as to smoothly connect the peripheral side faces betweenthe slopes across the apex. In each of the ridges 1 a, the apex isformed with being shifted toward the front side in the rotationaldirection. As described in the prior art example, with respect to theangles at which the slopes on both the sides of the apex protrude fromthe circumferential face A, therefore, the front angle θ₁₀ is closer toa right angle or steeper than the rear angle θ₂₀.

The valley 1 b which elongates along the circumferential face A of thedisk cutter 1 is formed between the ridges 1 a. As shown in FIG. 15 inwhich the circumferential face A that is within the same radius from theaxis of the disk cutter is developed to a plane, therefore, the angleformed by the valley 1 b and the front slope of the ridge 1 a that isrearward adjacent thereto is θ₁₀, and the angle formed by the valley andthe rear slope of the ridge 1 a that is forward adjacent thereto is θ₂₀.In FIG. 15, since the circumferential face A is shown with beingdeveloped to a plane, also the valley 1 b is shown in the same plane asthe circumferential face A. Small slopes 1 e are interposed respectivelybetween the valley 1 b and the slopes of the ridges 1 a that areadjacent thereto on both the sides. Each of the small slopes 1 e is aplane which connects the peripheral side face between the valley 1 b andthe slope of the ridge 1 a, and has an inclination angle at which thesmall slope is raised from the valley 1 b, and which is a half of theprotruding angle (θ₁₀ or θ₂₀) of the slope of the ridge 1 a from thecircumferential face A. Therefore, the small slopes 1 e are connectedalso to the slopes of the ridges 1 a at the same angle as the risingangle from the valley 1 b, and the slopes of the ridges 1 a protrudefrom the valley 1 b via the small slopes 1 e at the two-step bendingangles.

In the disk cutter 1, the grooves 1 c which are similar to those of theprior art example are formed in both the disk-like faces and in everyother valley 1 b. In the same manner as the prior art example shown inFIGS. 38 and 39, a large number of thus configured disk cutters 1 arearranged on a rotation shaft with being separated from each other toform a roll, and two rolls of the disk cutters 1 are verticallyarranged.

In the rotary expander of the second embodiment of the invention, themetal sheet 2 is passed between the upper and lower roll-like diskcutters 1, thereby forming the slits 2 a in the metal sheet 2. In themetal sheet 2, as shown in FIG. 2, the fence-like portion between theslits 2 a is pressed by the ridges 1 a of the upper and lower diskcutters 1 to protrude in a ridge-like shape. At this time, as shown inFIG. 16, small bent portions 2 h which are bent in two steps by thesmall slopes 1 e are formed between the node 2 c where the slits 2 a aredisconnected, and the fence-like portion (the wires 2 b) which protrudesin a ridge-like shape. The small bent portions 2 h are bent at both endsby an angle which is a (θ₁₁ or θ₂₁) in the prior art.

In the second embodiment of the invention, therefore, the fence-likeportion (the wires 2 b) between the slits 2 a of the metal sheet 2 canbe bent in two steps via the small bent portion 2 h by an angle which isa half of the conventional bending angle. When the metal sheet 2 isstretched to widen the slits 2 a to form meshes, therefore, a phenomenonthat the degree of cut of the slits 2 a in an end of the fence-likeportion is increased to shorten the length of the nodes 2 c shown inFIG. 43 or reduce the strength of the nodes to cause rupture does notoccur. As a result, edges of the meshes can be prevented from beingeasily corroded by electrolyte.

In the second embodiment of the invention, the case where each of thevalleys 1 b is configured by a face which extends along thecircumferential face A has been described. Alternatively, the valley 1 bmay be configured by a face other than that extending along thecircumferential face A, such as a flat face. In the case where thevalley 1 b is configured by a face extending along the circumferentialface A as in the embodiment or another curved face, the inclinationangle of the face is the inclination angle of a contacting face of aportion which is immediately in front of the portion connected to thesmall slope 1 e.

In the second embodiment of the invention, the case where the smallslope 1 e is formed in both the sides of each of the valleys 1 b hasbeen described. Alternatively, the small slope 1 e may be formed onlybetween each of the valleys 1 b and at least the front slope of theridge 1 a which is rearward adjacent to the valley in the rotationaldirection, because the slope of the rear ridge 1 a protrudes at thesteeper angle θ₁₀ with respect to the circumferential face A and hence acrack of corrosion in the node 2 c can be effectively prevented fromoccurring, even in a configuration in which the bending angle of theslope is simply divided into two steps. In the second embodiment of theinvention, the case where the small slope 1 e has an intermediateinclination angle between the slopes of the valley 1 b and the ridge 1 ahas been described. When the inclination angle is set to an arbitraryangle between the slopes of the valley 1 b and the ridge 1 a, thebending angle can be made gentle. However, the bending angles in boththe ends of the small slope 1 e are gentlest in the case where theintermediate inclination angle is employed as in the embodiment.

In the second embodiment of the invention, the case where the smallslope 1 e is interposed between the valley 1 b and the slope of theridge 1 a has been described. Alternatively, as shown in FIG. 17, acurved face 1 f may be interposed between the valley 1 b and the slopeof the ridge 1 a. All contact faces which are in contact with the curvedface 1 f must have an inclination angle between an inclination angle ofthe valley 1 b and that of the slope of the ridge 1 a. Preferably, thecurved face 1 f is rounded so that the inclination angle is closer tothe inclination angle of the valley 1 b as more approaching the valley 1b, and closer to that of the slope of the ridge 1 a as more approachingthe slope of the ridge 1 a. When the thus configured slope 1 e isinterposed between the valley 1 b and the slope of the ridge 1 a, thefence-like portion between the slits 2 a of the metal sheet 2 cansmoothly protrude in a ridge-like shape from the node 2 c. Therefore,cracks due to reduced strength caused by formation of angled bends canbe prevented from occurring, and edges of meshes can be prevented frombeing easily corroded by electrolyte.

Example 1

The case where the lead sheet 2 made of lead or a lead alloy is used asthe metal sheet 2, and the slits 2 a are formed and developed by usingthe disk cutter 1 of the prior art example in which the valley 1 b isdirectly connected to the slope of the ridge 1 a without interposing thesmall slope 1 e therebetween was compared with that where the slits 2 aare formed in the lead sheet 2 by using the disk cutter 1 of theembodiment in which the small slope 1 e is interposed between the valley1 b and the slope of the ridge 1 a. Results of the comparison are shownin Table 1.

TABLE 1 Development Life Inclination amount before performance angle ofsmall crack (100 in (100 in case slope (θ₁₀ = case of no of no small40°) small slope) slope) No small slope 100 100 Prior art example  5°105 101 Example 10° 109 105 Example 15° 116 113 Example 20° 122 116Example 30° 116 110 ExampleIn Table 1 above, in the case where the inclination angle of the valley1 b is set to 0° and that of the steep slope of the ridge 1 a which isin rear of the valley 1 b, i.e., the angle θ₁₀ is set to 40°, the priorart example of “no small slope”, and examples in which the inclinationangle of the small slope 1 e with respect to the steep slope is set to5°, 10°, 15°, 20°, or 30° were compared with one another in amount ofdevelopment which was conducted until crack occurred, and lifeperformance of a lead storage battery. Specifically, the slits 2 a wereformed in the lead sheet 2 by using a rotary expander having the diskcutters 1 of each kind, and the amount of development which wasconducted until crack occurred in the nodes 2 c was measured. The slits2 a were formed in the lead sheet 2 by using a rotary expander havingthe disk cutters 1 of each kind, and developed by a predetermined amountto form a grid, an active material was filled into the grid, and thegrid was then cured and dried to form a positive plate. The positiveplate was combined with a negative plate which was produced by aconventional method, and a separator which is configured mainly bymicroporous polyethylene, to produce a lead storage battery for anautomobile. The lead storage battery was subjected to a light-load lifetest according to JIS standard (D 5301) in a gaseous phase of 75° C.After the life test was ended, the battery was disassembled, and therates of crack portions in the higher- and lower-angle sides of the node2 c in the grid were investigated.

From the comparison results shown in Table 1, it has been seen that, inall the cases where the small slope 1 e is interposed, the developmentamount before the node 2 c cracks is larger than that in the prior artexample, and maximized in the case where the small slope 1 e has theinclination angle of 20° which is an intermediate inclination anglebetween the valley 1 b and the slope of the ridge 1 a, while becominglarger as being nearer to the inclination angle. Furthermore, it hasbeen seen that, in accordance with this, also the SAE life performanceat 75° C. is excellent.

As apparent from the above description, according to the method ofproducing a grid for a battery plate of the invention and the apparatusfor the method, a small slope or a curved face is interposed betweeneach of the valleys and the slope of each of the ridges in the diskcutter, the angled bend between the valley and the slope of the ridgecan be set to two steps so as to be gentle, or to be smoothly conducted.Therefore, the rising angle by which the fence-like portion between theslits of the metal sheet protrudes in a ridge-like shape can be madegentle, and the portion can be smoothly raised. Consequently, theportion can be prevented from being easily corroded by electrolyte,thereby preventing the capacity of a battery from being reduced, and thelife of the battery from being shortened.

Embodiment (3) of the Invention

Next, a third embodiment of the invention will be described withreference to the accompanying drawings.

The third embodiment corresponds to a modification of theabove-described second embodiment, and is also a preferable example ofmeans for solving above discussed Problem (2) to be solved.

FIGS. 18 and 19 show the third embodiment of the invention. FIG. 18 is apartial enlarged front view showing an inclined valley of a disk cutter,and FIG. 19 is a partial enlarged front longitudinal section viewshowing a fence-like portion between slits protruding in a ridge-likeshape in a metal sheet.

In a manner similar to the prior art example shown in FIGS. 37 to 50,also the third embodiment of the invention relates to the disk cutter 1of a rotary expander. The disk cutter 1 is a cutting tool in which alarge number of ridges 1 a protrude from the peripheral side face of athin disk-like steel plate. The ridges 1 a protrude at equal angularintervals from the peripheral side face of the disk cutter 1, and arearranged with forming a constant gap between adjacent ridges. As shownin FIG. 18 in which the circumferential face A that is within the sameradius from the axis of the disk cutter is developed to a plane, each ofthe ridges 1 a is formed so as to protrude in a ridge-like shape fromthe circumferential face A, and rounded. In each of the ridges 1 a, theapex of the ridge-like shape is formed with being shifted toward thefront side in the rotational direction. As described in the prior artexample, with respect to the angles at which the slopes on both thesides of the apex protrude from the circumferential face A, therefore,the front angle θ₁₀ is closer to a right angle or steeper than the rearangle θ₂₀ (hereinafter, for each of the ridges 1 a, the side of thefront angle θ₁₀ is referred to as “the higher-angle side”, and the sideof the rear angle θ₂₀ is referred to as “the lower-angle side”).

The valley 1 b in which the front side is inclined toward the centerwith respect to the circumferential face A of the disk cutter 1 isformed between the ridges 1 a. The valley 1 b is configured by a facewhich is obtained by rotationally displacing the curved face extendingalong the circumferential face A so as to incline the front side towardthe center, about the crossing line between the curved face and theslope of the rear ridge 1 a on the higher-angle side. Therefore, thevalleys 1 b is a face in which all contact faces contacting with thevalley 1 b are inclined toward the center by a constant angle as beingmore forward than the contact face which is centered at the rotationaxis of the disk cutter 1 and has the same angular position. At thistime, it is preferable to set the inclination angle of the valley 1 b to1° or more. Since FIG. 18 shows the circumferential face A withdeveloping the face to a plane, also the valley 1 b is shown as a planewhich is inclined by a constant angle with respect to thecircumferential face A. When the valley 1 b is inclined in this way, thebending angle θ₃₀ between the valley and the higher-angle side slope ofthe ridge 1 a which is rearward adjacent thereto is larger than theangle θ₁₀ with respect to the circumferential face A or becomes gentle.The bending angle θ₄₀ between the valley and the lower-angle side slopeof the ridge 1 a which is forward adjacent thereto is smaller than theangle θ₂₀ with respect to the circumferential face A or becomes steep.However, the angle θ₁₀ with respect to the circumferential face A isoriginally sufficiently closer to a right angle or steeper than theangle θ₂₀, and hence the angle θ₄₀ with respect to the valley 1 b iscloser to the angle θ₃₀ so as to reduce the difference.

In the disk cutter 1, the grooves 1 c which are similar to those of theprior art example are formed in both the disk-like faces and in everyother valley 1 b. In the same manner as the prior art example shown inFIGS. 38 and 39, a large number of thus configured disk cutters 1 arearranged on a rotation shaft with being separated from each other toform a roll, and two rolls of the disk cutters 1 are verticallyarranged. At this time, the upper and lower rollers of the disk cutters1 are placed in the same manner as the prior art example shown in FIG.39. In the embodiment, however, the valley 1 b is inclined, and hencethe rolls are placed respectively at levels which allow at least theportions of the faces of the valleys 1 b which are closest to the centerto slightly overlap with each other without forming a gap therebetween.

In the rotary expander of the third embodiment of the invention, themetal sheet 2 is passed between the upper and lower roll-like diskcutters 1, thereby forming the slits 2 a in the metal sheet 2. In themetal sheet 2, as shown in FIG. 19, the fence-like portion between theslits 2 a is pressed by the ridges 1 a of the upper and lower roll-likedisk cutters 1 to protrude in a ridge-like shape to be formed as thewires 2 b. At this time, the node 2 c in which the slits 2 a aredisconnected is obliquely formed by the valleys 1 b of the disk cutters1. As a result, the bending angle θ₃₁ with respect to the higher-angleside slope of the rear ridge is made gentle, and the bending angle θ₄₁with respect to the lower-angle side slope of the front ridge is madesteep, so that the difference between the angles is reduced. Thefence-like portions (the wires 2 b) between the slits 2 a which areadjacent to each other protrude respectively in opposite directions orupward and downward directions. Therefore, the fence-like portions onboth sides of the node 2 c are inclined respectively in oppositedirections or upward and downward directions, and hence the node 2 citself is in a twisted state.

In the embodiment, therefore, the fence-like portion between the slits 2a of the metal sheet 2 is prevented from being bent only in thehigher-angle side by a steep angle, and the bending angles θ₃₁ and θ₄₁of the higher- and lower-angle sides can be averaged. When the metalsheet 2 is stretched to widen the slits 2 a to form meshes, therefore,the phenomenon in the prior art that the degree of cut in only thehigher-angle side in the fence-like portion between the slits 2 a islarge and the length and strength of the node 2 c shown in FIG. 43 arereduced to cause rupture in edge portions does not occur. Consequently,edges of meshes can be prevented from being easily corroded byelectrolyte.

In the embodiment, the case where the valley 1 b is configured by a facewhich is obtained by rotationally displacing the curved face extendingalong the circumferential face A has been described. The valley may beconfigured by any kind of face as far as all contact faces contactingwith the valley 1 b are inclined toward the center as being more forwardthan the contact face which is in contact with the circumferential faceA at the same angular position. Alternatively, the face may be a curvedor flat face other than a face extending along the circumferential faceA. When the valley 1 b is a flat face which is inclined by a smallangle, there sometimes arises a case where only a front end portion ismore inclined toward the outer periphery as being more forward than thecontact face of the circumferential face A at the same angular position.Also in such a case, it is possible to attain the effect that thebending angle with respect to the higher-angle side slope of the rearridge 1 a is made gentle. In some cases, the portion between the valley1 b and the lower-angle side slope of the ridge 1 a which is forwardadjacent is rounded, or a small slope having an intermediate inclinationangle is interposed in the portion. Also in such cases, it is possibleto attain not only the effect that the bending angle with respect to thelower-angle side slope of the front ridge 1 a is made further gentle,but also the effect that the bending angle with respect to thehigher-angle side slope of the rear ridge 1 a is made gentle. Namely,the face contacting with the valley 1 b may be a face which is inclinedtoward the center as being more forward than the contact face that is incontact with the circumferential face A at the same angular position,excluding at least a front end portion of the valley 1 b.

In the embodiment, the case where the valley 1 b is configured so that aface contacting with the valley 1 b is inclined toward the center asbeing more forward than the contact face which is in contact with thecircumferential face A at the same angular position has been described.Alternatively, the face contacting with the valley 1 b may be configuredby a face which is more inclined toward the center as being more forwardthan a plane connecting together cross lines between the circumferentialface A and the slopes of the ridges 1 a on both the sides. In thealternative, even when the valley 1 b is a flat face which is inclinedby a small angle, a face which is surely inclined over a range to afront end portion is obtained.

Example 1

The case where the lead sheet 2 made of lead or a lead alloy is used asthe metal sheet 2, and the slits 2 a are formed and developed by usingthe disk cutter 1 of the prior art example in which the valley 1 b isnot inclined was compared with that where the slits 2 a are formed inthe lead sheet 2 by using the disk cutter 1 of the embodiment in whichthe valley 1 b is inclined. Results of the comparison are shown in Table2.

TABLE 2 Life performance (100 in Percentage Percentage case of of crackin of crack in inclination Inclination lower-angle higher- angle ofangle side angle side 0°) 0° 0% 30% 100 Prior art example 1° 0% 25% 105Example 3° 1% 19% 113 Example 5° 3% 12% 130 Example 8° 5% 6% 152 Example10°  6% 6% 147 Example

In Table 2 above, a prior art example in which the inclination angle ofthe valley 1 b is 0°, and examples in which the inclination angle is 1°,3°, 5°, 8°, or 10° were compared with each other with respect to thepercentages of crack in the higher- and lower-angle sides and lifeperformance of a lead storage battery. Specifically, the lead sheet 2was formed into a grid by using a rotary expander having the diskcutters 1 of each kind, an active material was filled into the grid, andthe grid was then cured and dried to form a positive plate. The positiveplate was combined with a negative plate which was produced by aconventional method, and a separator which is configured mainly bymacroporous polyethylene, to produce a lead storage battery for anautomobile. The lead storage battery was subjected to a light-load lifetest according to JIS standard (D 5301) in a gaseous phase of 75° C.After the life test was ended, the battery was disassembled, and therates of crack portions in the higher- and lower-angle sides of the node2 c in the grid were investigated.

From the comparison results shown in Table 2, it has been seen that, inthe prior art example, the percentage of crack in the higher-angle sideis high, and by contrast, in the examples, the percentage of crack inthe lower-angle side is slightly higher but that in the higher-angleside is greatly reduced as the inclination angle is larger, and thetotal percentage of crack is lower as the inclination angle is larger.Furthermore, it has been seen that, in accordance with this, also theSAE life performance at 75° C. is more improved as the inclination angleis larger, until the inclination angle has a certain large value.

As apparent from the above description, according to the method ofproducing a grid for a battery plate of the invention and the apparatusfor the method, the valley between the ridges of the disk cutter is moreinclined toward the center as being more forward. Consequently, thebending angle between the valley and the steep slope of the ridge thatis rearward adjacent thereto can be made large so as to be gentle. Whenslits are formed in a metal sheet, therefore, the node is inclined, andthe steep rising angle by which the fence-like portion between the slitsprotrudes in a ridge-like shape can be made gentle, so that the portioncan be prevented from being easily corroded by electrolyte, therebypreventing the capacity of a battery from being reduced, and the life ofthe battery from being shortened.

Embodiment (4) of the Invention

Next, a fourth embodiment of the invention will be described withreference to the accompanying drawings.

FIGS. 20 to 26 show the fourth embodiment of the invention. FIG. 20 is afront view showing the whole of a disk cutter, and a peripheral edge ofthe disk cutter in an enlarged manner, FIG. 21 is a partial enlargedperspective view showing inclined faces formed in peripheral side facesof ridges which are opposed across a valley of the disk cutter, FIG. 22is a partial enlarged side longitudinal section view showing a slitforming step of a rotary expander and illustrating a manner in whichwires of a metal sheet are twisted with being pressed by the inclinedfaces formed in ridges of disk cutters of upper and lower disk cutterrolls, FIG. 23 is a partial enlarged perspective view showing a metalsheet and illustrating a node formed in the slit forming step, and fourwires connected thereto, FIG. 24 is a partial enlarged perspective viewshowing another first configuration example of the inclined faces formedin peripheral side faces of ridges which are opposed across a valley ofthe disk cutter, FIG. 25 is a partial enlarged perspective view showinganother second configuration example of the inclined faces formed inperipheral side faces of ridges which are opposed across a valley of thedisk cutter, and FIG. 26 is a partial enlarged perspective view showinganother third configuration example of the inclined faces formed inperipheral side faces of ridges which are opposed across a valley of thedisk cutter.

In a manner similar to the prior art example, also the fourth embodimentof the invention relates to a rotary expander for producing a grid for abattery (lead storage battery) plate. As shown in FIG. 38, the metalsheet 2 is passed between the upper and lower disk cutter rolls to forma large number of zigzag slits 2 a in the metal sheet 2. The portionbetween the slits 2 a in the width direction of the lead sheet 2 isconfigured as the wire 2 b, and that between the slits in the advancingdirection is configured as the node 2 c.

In each of the disk cutter rolls, in the same manner as the prior artexample, a large number of the disk cutters 1 are arranged with forminga gap therebetween. However, the disk cutter 1 is configured in a mannerdifferent from the prior art example. In the disk cutter 1, as shown inFIG. 20, the ridges 1 a having a relatively long circumferential length,and the valleys 1 b having a relatively short circumferential length arealternately formed in a large number in the peripheral edge of a metaldisk over the whole circumference. In each of the valleys 1 b, aperipheral side face configured by a reference circumferential face of apredetermined radius and centered at the axis of the disk cutter 1 isformed in the same manner as the prior art example. The groove 1 c whichis opened in a peripheral side face of the valley 1 b is formed in aperipheral edge portion of one of disk faces in which valleys 1 b thatare adjacent to each other via the ridge 1 a are formed in an oppositelyreverse manner. Also in FIG. 20, the oval enlarged view shows thereference circumferential face in a form developed to a plane.

In each of the ridges 1 a of the disk cutter 1, a peripheral side facewhich protrudes in a ridge-like shape from the reference circumferentialface toward the outer periphery. As shown in the oval enlarged view ofFIG. 20, the peripheral side face of the ridge 1 a is formed in aridge-like shape in which the peripheral side face obliquely rises in asubstantially linear manner from the reference circumferential face thatis a peripheral side face of the valley 1 b toward the outer peripheralside, is curved in the apex of the ridge 1 a, and obliquely falls in asubstantially linear manner toward the inner peripheral side to returnto the reference circumferential face. The rising and falling portionsof the peripheral side face of the ridge 1 a are not evenly formed inthe rotational direction with respect to the apex of the ridge 1 a.Actually, the apex is shifted toward the front side in the rotationaldirection, so that the rising portion which is in the front side in therotational direction is a peripheral side face which is steeper than thefalling portion in the rear side. The configuration in which the apex ofthe ridge 1 a is shifted toward the front side in the rotationaldirection is identical with that of the prior art.

Inclined faces 1 g, 1 g are formed in the rising and falling portions ofthe peripheral side face of the ridge 1 a, respectively. As shown inFIG. 21, the inclined faces 1 g are formed respectively in ranges frommiddles of the rising and falling portions of the peripheral side facesof the ridges 1 a, to the valley 1 b, and, in the same manner as thegrooves 1 c, formed as faces which are alternately inclined in oppositedirections for each of the valleys 1 b. For each of the valleys 1 b, theinclined faces are more inclined toward the center of the rotation shaftof the disk cutter 1 as being nearer to the disk face (directed to theright lower side in FIG. 21) in which the groove 1 c opened in thevalley 1 b is formed, respectively in the falling portion of theperipheral side face of the ridge 1 a which is in the front side in therotational direction, and the rising portion of the peripheral side faceof the ridge 1 a which is in the rear side in the rotational direction(or in the falling and rising portions which are opposed to each otheracross the valley 1 b), the ridge portions being adjacent to both thesides of the valley 1 b. In the peripheral side face of a certain one ofthe ridges 1 a, therefore, the inclined face 1 g formed in the risingportion, and that formed in the falling portion are inclined in oppositedirections, respectively.

In the embodiment, the inclined face 1 g is configured by a planeenclosed by a triangle in which the vertexes are points A, B, and Cshown in FIG. 21. In this case, the point A is a point where, when thedistance (height) from the intermediate part of the edge of the fallingportion of the peripheral side face of the ridge 1 a shown in the rightupper side of FIG. 21 on the side of the disk face directed to the rightlower side in FIG. 21, i.e., the reference circumferential face that isa peripheral side face of the valley 1 b, to the apex of the ridge 1 ais indicated by H, a tangential line with a circumferential face of aradius which is larger by H/2 than the predetermined radius of thereference circumferential face, and the peripheral side face of theridge 1 a intersects the disk face. The point B is a point where theedge of the falling portion of the peripheral side face of the ridge 1 aon the side of the disk face directed to the left upper side in FIG. 21is in contact with the peripheral side face of the valley 1 b. The pointC is a point which is on the peripheral edge the disk face directed tothe right lower side in FIG. 21, and closer to the ridge 1 a along thereference circumferential face than a point O where the falling portionof the original peripheral side face of the ridge 1 a is in contact withthe original peripheral side face of the valley 1 b. Since the point Cis closer toward the ridge 1 a, the inclined face 1 g is inclined withrespect to the falling portion of the peripheral side face of the ridge1 a.

In the above, the inclined face 1 g formed in the right upper side ofthe valley 1 b shown in FIG. 21 has been described. Also the inclinedface 1 g formed in the left lower side of the valley 1 b shown in FIG.21 is configured by a plane enclosed by a similar triangle, and is aface which is inclined in the same direction with respect to theperipheral side face of the ridge 1 a. For another valley 1 b which isadjacent to the valley 1 b through the ridge 1 a, and which is not shownin FIG. 21, inclined faces 1 g, 1 g which are inclined in oppositedirections are formed.

When the metal sheet 2 is passed between disk cutter rolls using thedisk cutters 1 in which the inclined faces 1 g are formed, the metalsheet is vertically pressed by the inclined faces 1 g of the ridges 1 aof the disk cutters 1 as shown in FIG. 22, at the timing when the slits2 a are formed by the ridges 1 a, whereby the wires 2 b are deformed ina ridge-like shape while being twisted. The section shape is not arectangular shape but a parallelogram shape. In each of the wires 2 b,as shown in FIG. 23, the portion which is pressed by the inclined face 1g of the ridge 1 a, i.e., the end portion connected to the node 2 c (thedotted portion in FIG. 23) is formed with being twisted from thebeginning. The twisting direction of the end portion of the wire 2 bindicated by the arrow R of FIG. 23 is opposite to the direction inwhich the node 2 c connected to the end portion is twisted during thedeveloping process, i.e., the direction of the arrow F which has beendescribed in conjunction with FIG. 45. The relationship in which thetwisting directions of the arrows R and F are opposite to each other isapplied also to the two upper wires 2 b shown in FIG. 23. In the node 2c which is twisted in the direction of the arrow G in FIG. 45 during thedeveloping process, the wires 2 b connected to the node are formed withbeing twisted in the direction opposite to that of the arrow G.

According to the configuration, when the slits 2 a are formed in themetal sheet 2, the rotary expander of the embodiment deforms the wires 2b into a ridge-like shape in a state where the end portions of each ofthe wires 2 b are pretwisted by the inclined faces 1 g formed in theperipheral side faces of the ridges 1 a of the disk cutter 1. Moreover,the end portions of the wire 2 b are twisted in the direction oppositeto the direction in which the node 2 c is twisted during the process ofdeveloping the metal sheet 2. Even when the node 2 c is twisted duringthe developing process in which the metal sheet 2 is actually developed,therefore, the wires 2 b connected to the node receive torsion stress inwhich the previously applied twisting is canceled. In the wires 2 b,consequently, influence of torsion stress applied to the end portionscan be reduced, and the torsion stress can be prevented from beingconcentrated into the vicinity of the apex 2 e of the wire 2 b.

In the embodiment, the case where the point C of the inclined face 1 gis made closer to the ridge 1 a along the reference circumferential facethan the point O as shown in FIG. 21 has been described. Alternatively,as shown in FIG. 24, the point C may be made close toward the axis alongthe edge of the groove 1 c, i.e., a radial direction of the disk cutter1. In the case of FIG. 21, the peripheral side face of the valley 1 b iswidened by the area of the triangle BOC. When the inclined faces areconfigured as shown in FIG. 24, the inclined faces 1 g are naturallyconnected to the peripheral side face of the valley 1 b and the groove 1c, so that twisting applied to the end portions of the wire 2 b can besmoothed. In the case of FIG. 24, however, the peripheral side face ofthe valley 1 b is caused to extend along the side BC of the inclinedface 1 g by forming a tapered face in which the edge on the side of thedisk face where the groove 1 c is not formed coincides with thereference circumferential face and the radius is made smaller as beingnearer toward the disk face where the groove 1 c is formed.

Alternatively, as shown in FIG. 25, the point B of the inclined face 1 gin FIG. 24 may be moved to the edge of the opening of the groove 1 calong the reference circumferential face. In the alternative, althougheven the maximum width of the inclined face 1 g is only about one halfof the width of the peripheral side face of the ridge 1 a, the torsionstress can be reduced even in the case where about a half portion of thewidth of the wire 2 b is pretwisted instead of the whole width.

Since the groove 1 c for forming the node 2 c in the metal sheet 2 isused for preventing the slits 2 a from being formed in the metal sheet2, by means of the gap between the groove and the groove 1 c of theopposed disk cutter 1, the groove 1 c is not always required to berectangular. As shown in FIG. 26, for example, the groove 1 c may beformed by chamfering the peripheral side face of the valley 1 b, so asto be configured by a face through which edge sides of the inclinedfaces 1 g on both sides are connected to each other.

The peripheral side faces of the ridges 1 a of the disk cutters 1 whichare alternately opposed are pressed to each other through the metalsheet 2, thereby forming the slits 2 a in the metal sheet 2. Therefore,it is preferable to set the angle of the edge formed by the peripheralside face of the ridge 1 a and the corresponding one of the disk facesof the disk cutters 1, to be as acute as possible, and usually to 90°.When the inclined face 1 g is formed in the peripheral side face of theridge 1 a, however, the edge between the inclined face 1 g and the diskface inevitably has an obtuse angle. When the angle is excessivelylarge, the metal sheet 2 cannot be surely cut and the slits 2 a are notformed. Therefore, the inclination angle of the inclined face 1 g mustbe set so as not to be excessively large. Preferably, the inclinationangle with respect to the reference circumferential face is set to beequal to or smaller than 40°, so that the angle of an edge between theinclined face and the disk face can be set to 60° or more, therebyenabling the slits 2 a to be surely formed in the metal sheet 2.

In order to prevent torsion stress from being concentrated into thevicinity of the apex 2 e of the wire 2 b, preferably, the inclined face1 g is formed with starting from a position which is as near as possibleto the apex of the ridge 1 a. Therefore, it is preferable to set thepoint A of the inclined face 1 g which is nearest to the apex to a levelthat is at least one third of the height H of the apex. In theembodiment, the point A is located at a level that is about a half ofthe height H of the apex. It is a matter of course that the inclinedface 1 g may be formed with starting from a position which is nearer tothe apex. When the inclined face 1 g is formed so as to extend to aposition which is very near to the apex of the ridge 1 a, however, theinclined face 1 g abuts against the metal sheet 2 at the timing whencutting for the slits 2 a is initially formed in the metal sheet, andhence the edge with respect to the disk face has an obtuse angle,thereby causing the possibility that the cutting operation cannot besmoothly started.

In the embodiment, the case where the inclined face 1 g is formed as aflat face has been described. However, the inclined face is not alwaysnecessary to be flat, as far as the face more approaches the axis of thedisk cutter 1 as being nearer to the disk face on the side where thegroove 1 c of the adjacent valley 1 b is formed, and may be formed by acurved face or a plurality of flat faces. The inclined face 1 g is notrequired to be a triangle surrounded by three vertexes.

In the embodiment, the rotary expander in which the metal sheet 2 ispassed between upper and lower or two disk cutter rolls has beendescribed. The disk cutter rolls can be arranged in an arbitrary manner.The invention can be similarly applied also to a rotary expander inwhich the metal sheet 2 is passed between three or more disk cutterrolls that are opposedly arranged.

In the embodiment, the case where the metal sheet 2 is processed toproduce a grid which is to be used in a battery plate of a lead storagebattery has been described. The invention is not restricted to a leadstorage battery, and can be applied also to a battery of any kind as faras a similar grid is used as a current collecting member of a batteryplate. A grid can be produced by using a metal sheet of an appropriatematerial which corresponds to the kind of the battery.

Example 3

The grids of the embodiment and the prior art example were produced fromthe metal sheets (lead sheet) 2 by using the disk cutter 1 which hasbeen described in the embodiment, and the disk cutter 1 which has beendescribed in the prior art example. The rate of rupture was investigatedby observing in detail the vicinities of apexes 2 e of the wires 2 bafter development. An active material was filled into the grids of theembodiment and the prior art example, and the grids were then cured anddried to form positive plates. The plates were incorporated into leadstorage batteries (Type 55D23 of JIS) for an automobile, and a givenamount of diluted sulfuric acid of a predetermined specific gravity waspoured and formation was performed to complete the batteries. Anovercharge test according to JIS was conducted to test the lifeperformance, and the breakage rate of the wires 2 b after the test wasinvestigated. In all the lead storage batteries, a conventional platewas used as the negative plate, and a separator which is configuredmainly by microporous polyethylene was interposed between the plates.

In the ridge 1 a of the disk cutter 1 of the embodiment, the inclinedface 1 g was configured as a triangular flat face such as shown in FIG.21. Grids in which the height from reference circumferential face thatis a peripheral side face of the valley 1 b to the inclination startingposition (point A) of the inclined face 1 g which is nearest to the apexis 20%, 50% (H/2), or 70% of the height H of the apex of the ridge 1 awere produced. In principle, the inclination angle of the inclined face1 g with respect to the reference circumferential face was set to 30°.In grids in which the inclination starting position of the inclined face1 g is set to 70%, however, a plurality of grids were produced in arange of 10° to 50°.

Results of comparisons between the embodiment and the prior art exampleare shown in Table 3. In the specimen which is shown in the last row ofTable 3, and in which the inclination angle of the inclined face 1 g isset to 50°, a grid could not be produced, and hence it was impossible tocheck and test the specimen, because the edge between the inclined face1 g and the disk face of the disk cutter 1 was so obtuse that the metalsheet 2 could not be cut and the slits 2 a were not formed. From this,it has been seen that it is preferable to set the inclination angle ofthe inclined face 1 g to 40° or less.

TABLE 3 Incli- Rate of Life per- Breakage nation Angle of rupture informance rate starting inclined vicinity (prior of wires position faceof apex art = 100) after test Remarks None None 40 100 40 Prior artexample 20% 30° 30 115 30 Example 50% 30° 15 130 15 Example 70% 30° 5140 0 Example 70% 10° 24 118 25 Example 70% 20° 15 129 12 Example 70%40° 5 115 0 Example 70% 50° — — — —

As a result of the comparison, it has been confirmed that the rate ofrupture in the vicinity of the apex 2 e in all the examples is lowerthan that of the prior art example or 40% and all the examples areeffective in suppression of occurrence of rupture. In all the examples,with respect to the life performance and the breakage rates of the wires2 b after test, the life was longer and the breakage rate was lower thanthose of the prior art example in accordance with the reduction of therate of rupture. In the specimen in which the inclination startingposition of the inclined face 1 g was set to 20%, the difference withrespect to the prior art example is relatively small, and hence it hasbeen seen that it is preferable to set the inclination starting positionto a position which is at least one third (about 33%) or higher of theheight H of the apex of the ridge 1 a.

As apparent from the above description, according to the grid for abattery plate of the invention and the apparatus for the grid, the wiresof the metal sheet are pressed into a ridge-like shape in a twistedstate by the inclined faces formed in the peripheral side faces of theridges of the disk cutter. Therefore, concentration of torsion stress ofthe opposite direction in the vicinity of the apexes of the wires andgenerated during the developing process can be suppressed. As a result,corrosion and a crack of corrosion can be prevented from occurring inthe wires of the grid, so that a failure of a battery can be suppressedfrom occurring and the life of a battery can be prolonged.

Embodiment (5) of the Invention

FIGS. 27 to 29 show a fifth embodiment of the invention. FIG. 27 is alongitudinal section view showing a first example of formation of a nodein the metal sheet 2 by a disk cutter, FIG. 28 is a longitudinal sectionview showing a second example of formation of a node in the metal sheet2 by a disk cutter, and FIG. 29 is a longitudinal section view showing athird example of formation of a node in the metal sheet 2 by a diskcutter.

As shown in FIG. 27( a), two disk cutter rolls each configured by alarge number of such disk cutters 1 are vertically arranged, and a leadsheet 2 is passed between the rolls, thereby forming slits 2 a and thenodes 20. At this time, the upper and lower disk cutter rolls are placedrespectively at levels which allow the valleys 1 b of the upper andlower disk cutters 1 to slightly overlap with each other. In at leastboth disk faces of the peripheral side face of the disk cutter 1 whichis not a ridge 1 a, as shown in FIG. 27( b), a chamfered portion 1 m isformed so as to be lowered toward each of the grooves 1 c which arealternately disposed in the width direction. In the disk cutter 1,specifically, the ridges 1 a, and the valley 1 b between the ridges 1 aare formed, and the chamfered portion 1 m is disposed over a range fromthe peripheral side face of the valley 1 b to the groove 1 c. Thechamfered portion 1 m is lowered as moving from the peripheral side faceof the valley 1 b toward the groove 1 c. A new ridgeline 1 j which isformed on the side of the groove 1 c does not damage the node 2 c of themetal sheet 2.

As shown in FIG. 28( a) and FIG. 28( b) which is a perspective viewshowing the vicinity of the valley 1 b of the disk cutter 1, thechamfered portion 1 m which is formed from the peripheral side face ofthe valley 1 b of the disk cutter 1 to the groove 1 c may be furtherchamfered to form a chamfered portion 1 n in the ridgeline 1 j betweenthe chamfered portion 1 m to the groove 1 c. Alternatively, as shown inFIGS. 29( a) and 29(b), a curved face 1 p may be disposed in theperipheral side face of the valley 1 b. The chamfered portions 1 m and 1n, or the curved face 1 p is effective in improvement of the strengthand suppression of local corrosion which are due to suppression ofrupture of the node 2 c formed in the metal sheet 2.

In the outermost peripheral side face where the groove 1 c is disposed,a certain inclination with respect to the surface of the metal sheet 2which is being passed between the rolls is provided to the peripheralside face, so that a peripheral side face which is substantiallyparallel to the metal sheet 2 is eliminated. As apparent from comparisonbetween FIG. 46, and FIGS. 27 to 29, in the conventional method shown inFIG. 46, excessive stress is applied to the bent portions of the node 2c of the metal sheet 2, and, when the disk cutter 1 of the inventionshown in FIGS. 27 to 29 is used, reduced stress is applied to the node 2c of the metal sheet 2. When the disk cutter 1 of the invention is used,therefore, the strength of the node 2 c can be improved and localcorrosion can be suppressed irrespective of the shapes of the otherportions of the disk cutter 1.

Example 4

Next, a method of producing an expand grid will be described.

A plurality of slits which are parallel to one another were formedintermittently and in a zigzag pattern along the longitudinal directionof a lead sheet 2 that is the metal sheet 2. Thereafter, the sheet wasdeveloped in the width direction to attain a predetermined dimension toform meshes, thereby producing a grid for a battery plate (see, forexample, FIG. 38). An active material was filled into grids which wereproduced by this method, and the grids were then cured and dried to formpositive plates. The positive plates, negative plates which were formedby a usual method, and separators which are configured mainly bymicroporous polyethylene were combined to one another to produce leadstorage batteries (Type 55D23) for an automobile. Then, a given amountof diluted sulfuric acid of a predetermined specific gravity was pouredinto the batteries, and formation was performed to complete thebatteries.

Batteries having grids that were produced by using the disk cutters 1 inwhich the angle θ (FIG. 4) formed by the peripheral side face notconstituting the ridge 1 a and the disk face 3 is changed in a range of90 to 60°, and those having grids that were produced by using the diskcutters 1 in which the portion between the peripheral side face and thedisk face 3 where the groove 4 is formed is chamfered and various kindsof flat or curved faces are formed were subjected to a light-load lifetest according to JIS standard (D 5301) in a gaseous phase of 75° C.After the life test was ended, the batteries were disassembled, and therate of crack of corrosion due to rupture in the node 2 c wasinvestigated (Table 4).

TABLE 4 Percentage of Life Section crack in performance No. view Angle θnode (%) (100 in No. 1) Remarks 1 FIG. 46 90 5.0 100 Prior art example 2FIG. 27 85 4.6 105 Example 3 FIG. 27 75 3.2 113 Example 4 FIG. 27 65 2.8122 Example 5 FIG. 27 60 2.8 123 Example 6 FIG. 28 75 2.2 135 Example 7FIG. 29 75 2.1 143 Example

From the results shown in Table 4, is has been seen that, in expandgrids produced by using the disk cutter according to the invention, thepercentage of crack in nodes is suppressed as compared with the priorart example or No. 1 in which the flat portion forms an angle of 90°.Furthermore, it has been seen that, in accordance with this, also theSAE life performance at 75° C. is improved by forming an angle.

Embodiment (6) of the Invention

Hereinafter, a sixth embodiment of the invention will be described withreference to the accompanying drawings.

FIGS. 30 to 36 show the sixth embodiment of the invention. FIG. 30 is apartial enlarged front longitudinal section view showing a process offorming slits in a metal sheet (including a lead sheet) by disk cuttersof upper and lower disk cutter rolls, FIG. 31 is a side view showing theconfiguration of an endmost disk cutter, FIG. 32 is a partial enlargedperspective view showing the configuration of the endmost disk cutter,FIG. 33 is a partial enlarged perspective view showing the vicinity ofan endmost node in a grid which is obtained by developing slits formedin a metal sheet, FIG. 34 is a partial enlarged front longitudinalsection view showing a process of forming slits in a metal sheet byusing an endmost disk cutter in which inclined faces are formed inperipheral side faces of ridges, FIG. 35 is a partial enlarged frontlongitudinal section view showing a process of forming slits in a metalsheet by using an endmost disk cutter in which peripheral side faces ofvalleys are configured as a circumferential face, and FIG. 36 is apartial enlarged front longitudinal section view showing a process offorming slits in a metal sheet by using an endmost disk cutter in whichperipheral side faces of valleys are recessed.

In a manner similar to the prior art example, also the embodimentrelates to a rotary expander for producing a grid for a battery plate ofa lead storage battery. In the rotary expander, as shown in FIG. 38, themetal sheet 2 is passed between the upper and lower disk cutter rolls toform zigzag slits 2 a in the metal sheet 2. The upper disk cutter rollis configured in the same manner as the prior art example. The lowerdisk cutter roll has the same configuration as the prior art in whichthe endmost disk cutters 4 are disposed at both the ends of a largenumber of the disk cutters 1, but the configuration of the endmost diskcutters 4 is different from that of the prior art example.

In the same manner as the prior art example, also in each of the endmostdisk cutters 4 in the embodiment, as shown in FIGS. 31 and 32, theridges 4 a and the valleys 4 b are alternately arranged in theperipheral edge. However, the ridges 4 a and the valleys 4 b in theendmost disk cutter 4 show the peripheral edge corresponding to theridges 1 a and the valleys 1 b in the disk cutter 1 placed in the samedisk cutter roll, and do not always have a ridge-like shape or avalley-like shape. Specifically, a peripheral side face configured by areference circumferential face of a predetermined radius and centered atthe axis of the endmost disk cutter 4 is formed in the ridge 4 a, andthe valley 4 b is not formed as a concave portion between the ridges 4a. Unlike the prior art example, the groove 4 c is not formed in each ofthe valleys 4 b, an inward inclined face 4 d which is a peripheral sideface recessed toward the center from the reference circumferential face,and which is inward inclined is formed in each of the valleys 4 b(endmost node forming valleys) on one side which are alternatelyarranged, and an outward inclined face 4 e which is outward inclined isformed in each of the valleys 4 b on the other side. The peripheral sideface of the valley 4 b on the one side forms the inward inclined face 4d configured by a part of a tapered face wherein the portion contactingwith the outer disk face (the rear face in FIG. 31, and the right frontface in FIG. 32) of the endmost disk cutter 4 coincides with acircumferential face which is centered at the axis of the endmost diskcutter 4, and in which the radius is smaller than the predeterminedradius of the reference circumferential face by 50% of the thickness ofthe metal sheet 2. The radius of the tapered face is smaller as furthermoving from the portion toward the inner disk face (the front face inFIG. 31, and the left rear face in FIG. 32). In the valley 4 b on theone side, a peripheral side face that is recessed by one step from theridges 4 a which are adjacent on both the sides, and in which aperipheral side face is configured by the reference circumferential faceis formed, and the peripheral side face is configured by the inwardinclined face 4 d which is more inclined toward the center as beingnearer the inner disk face of the endmost disk cutter 4. The inwardinclined face 4 d is not always required to be a part of a tapered face,and may be a flat face or a curved face of another kind depending on thecircumstances of the process or the like, as far as the face is recessedfrom the peripheral side face of the ridge 4 a and inward inclined.

Each of the valleys 4 b (the valleys other than the endmost node formingvalleys) on the other side of the endmost disk cutter 4 forms theoutward inclined face 4 e configured by a part of a tapered face whereinthe portion contacting with the inner disk face of the endmost diskcutter 4 coincides with the reference circumferential face of thepredetermined radius, and in which the radius is smaller than thepredetermined radius as further moving from the portion toward the outerdisk face of the endmost disk cutter 4. Therefore, the valley 4 b on theother side has a shape where the outermost diameter is equal to that ofthe ridges 4 a which are adjacent on both the sides, and in which aperipheral side face configured by the reference circumferential face isformed, and the outward inclined face 4 e is formed by obliquely cuttingaway in the outer disk face. Also the outward inclined face 4 e is notalways required to be a part of a tapered face, and may be a flat faceor a curved face of another kind depending on the circumstances of theprocess or the like, as far as the face is more inclined toward thecenter than the peripheral side face of the predetermined radius asbeing nearer to the outer disk face.

The thus configured endmost disk cutters 4 are placed at the ends of thelower disk cutter roll so as to be outward juxtaposed with the usualdisk cutters 1 at the ends of the upper disk cutter roll, respectively.The phase in the rotational direction is adjusted so that the valley 4 bwhich is an endmost node forming valley of the endmost disk cutter 4 isopposed at the upper end via the metal sheet 2 to the valley 1 b of thedisk cutter 1 of the upper disk cutter roll in which the groove 1 c isformed in the opposed face. The metal sheet 2 is transported so as to bepassed between the upper and lower disk cutter rolls. At this time,conventionally, the metal sheet 2 is transported with being placed onthe transportation face which coincides with the cutting plane S betweenthe upper and lower disk cutter rolls.

By contrast, in the embodiment, the transportation face is set to belower than the cutting plane S by 50% of the thickness of the metalsheet 2. Conventionally, the cutting plane S of the upper and lower diskcutter rolls is set so as to coincide with the transportation face forthe metal sheet 2, i.e., the lower face of the metal sheet 2. Bycontrast, in the embodiment, the cutting plane S of the upper and lowerdisk cutter rolls is set so as to coincide with the middle portion ofthe thickness of the metal sheet 2 transported on the transportationface. The cutting plane S is a plane in which the distances from theaxes of the upper and lower disk cutter rolls are equal to each other.The predetermined radius of the reference circumferential faceconstituting the peripheral side face of the valley 1 b of each of theupper and lower disk cutters 1 is slightly larger than the distance fromthe axis to the cutting plane S. When the peripheral side face of thevalley 1 b of the upper disk cutter 1 is at the lower end, theperipheral side face slightly downward exceeds the cutting plane S, andthe peripheral side face of the valley 1 b of the lower disk cutter 1,that of the ridge 4 a of the endmost disk cutter 4, and the outermostperipheral end of the peripheral side face of the valleys 4 b of theendmost disk cutter 4 other than the endmost node forming valleysslightly upward exceed the cutting plane S.

When the metal sheet 2 is passed between the upper and lower disk cutterrolls, in the case where the valleys 1 b of the upper and lower diskcutters 1 overlap with each other in the cutting plane S, as shown inFIGS. 30( a) and 30(c), in the portions of the upper and lower adjacentdisk cutters 1 where the grooves 1 c face each other in oppositedirections, the metal sheet 2 is cut so that the slits 2 a are formed,and, in the portions where the grooves 1 c face each other, the metalsheet 2 is not cut and the nodes 2 c are formed. In the case where thevalley 4 b of the endmost disk cutter 4 is an endmost node formingvalley, i.e., the valley faces the groove 1 c of the adjacent upper diskcutter 1 (the left end in FIG. 30( a), and the right end in FIG. 30(c)), the endmost node 2 f connected to the frame portion 2 g of themetal sheet 2 is formed. In the endmost node 2 f, one end in the widthdirection of the metal sheet 2 (the left one in FIG. 30( a), and theright one in FIG. 30( c)) is directly connected to the frame portion 2g, and the other end is cut by the valley 1 b of the extreme end diskcutter 1 in the upper disk cutter roll, and also by the valley 1 b ofthe extreme end disk cutter 1 in the lower disk cutter roll excludingthe endmost disk cutter 4. The other end is pressed substantially to thecutting plane S by the valley 1 b of the upper disk cutter 1. In themetal sheet 2 which is transported on the transportation face,therefore, the other end of the endmost node 2 f is deformed with beingdownward pressed by 50% of the sheet thickness. By contrast, in the samemanner as the prior art, in the usual node 2 c, the one and other endsare vertically pressed while exceeding the same cutting plane S, andhence deformation of upward and downward directions and 100% or more ofthe sheet thickness occurs. In the endmost nodes 2 f, moreover, theportion which is above the valley 4 b of the endmost disk cutter 4 isgently bent from the transportation face along the inward inclined face4 d, and hence the other end is further gently deformed.

In the case where the valley 4 b of the endmost disk cutter 4 is not anendmost node forming valley, i.e., the valley faces the groove 1 c ofthe valley 1 b of the adjacent upper disk cutter 1 (the right end inFIG. 30( a), and the left end in FIG. 30( c)), the end of the frameportion 2 g of the metal sheet 2 is cut by means of the valley 1 b ofthe extreme end disk cutter 1 in the upper disk cutter roll. In the endof the frame portion 2 g, moreover, the portion which is above thevalley 4 b of the endmost disk cutter 4 is gently bent from thetransportation face along the outward inclined face 4 e.

In the case where the ridges 1 a of the upper and lower disk cutters 1overlap with each other, as shown in FIG. 30( b), the metal sheet 2 iscut by the adjacent upper and lower disk cutters 1 to form the slits 2a, and the wires 2 b between the slits 2 a are vertically pressed by theridges 1 a of the disk cutters 1. In the same manner as the prior art,the wires 2 b are pressed in a vertical ridge-like shape along thetransportation direction of the metal sheet 2. The metal sheet 2 abovethe ridge 4 a of the endmost disk cutter 4 is cut by the upper diskcutter 1 which is inward adjacent, to be formed as an end of the frameportion 2 g, and upward pressed by the ridge 4 a to the cutting plane Sby 50% of the sheet thickness.

The metal sheet 2 in which the many slits 2 a are formed as describedabove is stretched toward both the sides in the width direction in thesubsequent step of the rotary expander. As a result, as shown in FIG.33, the slits 2 a are widened so as to form meshes, whereby alattice-like grid is formed in which the nodes 2 c and the endmost nodes2 f are connected to one another by four wires 2 b that are obliquelydrawn out. In the same manner as FIG. 50, also in FIG. 33, twist of thenode 2 c and the wire 2 b is omitted and the grid is diagrammaticallyshown.

According to the configuration, the vertical deformation of the endmostnodes 2 f in the metal sheet 2 is about a half of the sheet thickness.Therefore, concentration of stress in the endmost nodes 2 f is reduced.Even after the wire 2 b is obliquely pulled as a result of development,corrosion or heat generation hardly occurs in the endmost nodes 2 f, andthere is little chance of breakage of the wire 2 b as compared with theusual node 2 c. Since the wire 2 b which is closest to the frameportions 2 g of the metal sheet 2 is hardly broken, it is possible tosurely prevent the capacity of a lead storage battery from being largelyreduced.

In the embodiment, the case where the outermost radius of the valley 1 bthat is the endmost node forming valley is smaller than thepredetermined radius by 50% of the thickness of the metal sheet 2 hasbeen described. However, this difference is not restricted to 50% of thesheet thickness as far as the outermost radius is smaller than thepredetermined radius. As the degree by which the outermost radius isreduced from the predetermined radius is smaller, the amount of thevertical deformation of the endmost nodes 2 f is larger. By contrast,when the degree by which the outermost radius is smaller than thepredetermined radius is large, the vertical level difference withrespect to the position where the metal sheet 2 is cut in the valleys 1b other than the endmost node forming valleys becomes excessively large.When the outermost radius is smaller than the predetermined radius by100% or more of the sheet thickness, the peripheral side face of thevalley 1 b that is the endmost node forming valley cannot support theendmost node 2 f of the metal sheet 2. Therefore, it is preferable toset the outermost radius of the valley 1 b that is the endmost nodeforming valley, to be smaller than the predetermined radius by a degreein a range from 30% or more to 70% or less of the thickness of the metalsheet 2.

In the embodiment, the case where the peripheral side face of the ridge4 a of the endmost disk cutter 4 is used as the referencecircumferential face has been described. Alternatively, as shown in FIG.34, the peripheral side face of the ridge 4 a may be formed as aninclined face similar to the outward inclined face 4 e of the valley 4 bother than the endmost node forming valleys. In the alternative, theperipheral side faces of the ridge 4 a of the endmost disk cutter 4 andthe valley 4 b other than the endmost node forming valleys constitutethe same inclined face, and the inward inclined face 4 d which isinclined in the opposite direction is formed only in the peripheral sideface of the valley 4 b that is the endmost node forming valley.

In the embodiment, the case where the inward inclined face 4 d and theoutward inclined face 4 e are formed in the peripheral side faces of thevalleys 4 b of the endmost disk cutter 4 has been described.Alternatively, as shown in FIG. 35, each of the peripheral side faces ofthe valleys 4 b may be configured by a circumferential face. In FIG. 35,the peripheral side face of the valley 4 b (the left end in FIG. 35)that is the endmost node forming valley is configured by acircumferential face of a radius which is smaller than the predeterminedradius by 100% of the sheet thickness, and the peripheral side face ofthe valley 4 b (the right end in FIG. 35) other than the endmost nodeforming valleys is the reference circumferential face of thepredetermined radius. For example, the peripheral side face of thevalley 4 b that is the endmost node forming valley may be configured bya circumferential face of a radius which is smaller than thepredetermined radius of the reference circumferential face by 50% of thesheet thickness. In this case, the endmost node 2 f is abruptly changedin a small range as compared with the case where the inward inclinedface 4 d is formed as in the embodiment. Although the amount of verticaldeformation of the endmost node 2 f is identical, the node is abruptlychanged in a smaller range in the axial direction of the disk cutterroll. In the embodiment, the groove 4 c is not formed in the endmostdisk cutter 4. In the case where the groove 4 c is formed also in theendmost disk cutter 4 as in the prior art, the inner side of theperipheral side face of the valley 4 b stepwise sinks. Even when theperipheral side face is configured by a circumferential face of a radiuswhich is smaller than the predetermined radius of the referencecircumferential face by 50% of the sheet thickness, therefore, theendmost node 2 f is not abruptly deformed. Namely, the step due to thegroove 4 c allows the metal sheet 2 to be gently deformed, in the samemanner as the inward inclined face 4 d and the outward inclined face 4 ein the valleys 4 b in the embodiment.

As described above, the peripheral side face of the valley 4 b that isthe endmost node forming valley in the endmost disk cutter 4 isrequested only to have the outermost radius which is smaller than thepredetermined radius, and not required to be a circumferential face. Theperipheral side face may be a flat face which extends substantiallyalong the circumferential face, a tapered face as in the embodiment, ora flat inclined face which extends substantially along the tapered face.Alternatively, the peripheral side face may have a step-like shape as inthe case where the groove 4 c is formed, or may be an arbitrary curvedface or a face of another kind. By contrast, in the valley 4 b otherthan the endmost node forming valleys, in order to cut the metal sheet 2in combination with the valley 1 b of the upper disk cutter 1, at leastthe outer radius of the inner end must be larger than the predeterminedradius and exceed the cutting plane S. As far as the conditions aresatisfied, the valley 4 b other than the endmost node forming valleysmay be configured by any kind of face.

In the embodiment, the case where the peripheral side face of the ridge4 a of the endmost disk cutter 4 is the reference circumferential faceof the predetermined radius has been described. Alternatively, as shownin FIG. 36, the peripheral side face of the ridge 4 a may be configuredby a circumferential face of a radius which is smaller than thepredetermined radius by 50% of the sheet thickness. In the alternative,the peripheral side face of the ridge 4 a has a radius which is equal tothe outermost radius of the outer end of the inward inclined face 4 d ofthe valley 4 b that is the endmost node forming valley in theembodiment. Also the ridge 4 a must cut the metal sheet 2 in combinationwith the ridge 1 a of the upper disk cutter 1. Since the ridge 1 a ofthe upper disk cutter 1 downward protrudes in a ridge-like shape, theperipheral side face of the ridge 4 a of the lower disk cutter 1 can beformed as such a circumferential face of a radius which is smaller thanthe predetermined radius. However, the amount of the downward protrusionin both the basal areas of the ridge 1 a of the upper disk cutter 1 issmall, and hence there arises the possibility that, in the areas, theradius of the peripheral side face of the ridge 4 a must be increased inorder to cut the metal sheet 2.

In the embodiment, the case where the endmost disk cutters 4 are placedrespectively at both the ends of the lower disk cutter roll has beendescribed. Alternatively, one or both of the endmost disk cutters 4 maybe placed in one or both ends of the upper disk cutter roll. Two or morepaired disk cutter rolls may be used. For example, the metal sheet 2 canbe passed through an arrangement of three disk cutter rolls.

In the embodiment, the case where the wires 2 b connected to the endmostnodes 2 f in the metal sheet 2, and those connected to the other nodes 2c are formed so as to have the same thickness has been described.Alternatively, the wires 2 b connected to the endmost nodes 2 f may beformed so as to be particularly thicker, so that the wires 2 b are morehardly broken.

In the embodiment, the case where the metal sheet 2 is processed toproduce a grid which is to be used in a battery plate of a lead storagebattery has been described. The invention is not restricted to a leadstorage battery, and can be applied also to a battery of any kind as faras a similar grid is used as a current collecting member of a batteryplate. A grid can be produced by using a metal sheet of an appropriatematerial which corresponds to the kind of the battery.

Example 5

By using rotary expanders in which the endmost disk cutters 4 of theembodiment, or the endmost disk cutter 4 of the prior art example areplaced at the ends of the lower disk cutter roll, the slits 2 a wereformed in the metal sheets 2, comparisons were then conducted. Resultsof the comparisons are shown in Table 5

TABLE 5 Ratio of sheet thick- Breakage rate ness after slitting Life ofendmost node Recess in Inclined to original sheet performance aftercorrosion test valley (%) face thickness (%) (prior art = 100) (rate ofcrack) (%) Remarks 0 None 60 100 42 Prior art example 10 None 69 103 35Example 30 None 80 136 12 Example 50 None 90 152 0 Example 70 None 83141 13 Example 100 None 63 110 37 Example 50 Formed 93 165 0 Example

As the metal sheet 2, a lead sheet of a thickness of 1.0 mm was used.The endmost disk cutters 4 configured in the following manner were used.In the prior art example, the peripheral side face of the valley 4 bcoincides with the reference circumferential face of the predeterminedradius (namely, in the prior art example, the valley 4 b is recessed by0% of the thickness of the lead sheet 2). In the examples, theperipheral side face of the valley 4 b is configured by acircumferential face which is recessed from the referencecircumferential face of the predetermined radius by 10% (0.1 mm), 30%(0.3 mm), 50% (0.5 mm), 70% (0.7 mm), or 100% (1.0 mm) of the thicknessof the lead sheet 2. In the example, the outermost end of the peripheralside face of the valley 4 b is recessed by 50% of the thickness of thelead sheet 2, and the inward inclined face 4 d of 30° is formed in theperipheral side face. The interval distance between the upper and lowerdisk cutter rolls was fixed.

In each of the lead sheets 2 in which the slits 2 a were formed by theprior art example and the examples, after development to a grid, thethickness of the thinnest part in the endmost node 2 f was measured, andthe ratio of the sheet thickness to the original thickness of the leadsheet 2 was calculated. An active material was filled into the grids,and the grids were then cured and dried to form positive plates. Theplates were incorporated into lead storage batteries (Type 55D23 ofJIS). An overcharge test according to JIS was conducted to test the lifeperformance, and the breakage rate of the wires 2 b after the test wasinvestigated. In all the lead storage batteries, a conventional platewas used as the negative plate, and a separator which is configuredmainly by macroporous polyethylene was interposed between the plates.

As a result of the comparison test, it has been confirmed that, in allof the grids produced by the examples, the sheet thickness ratio of theendmost node 2 f is larger than that of the prior art example, andelongation of the lead sheet 2 is suppressed. It has been confirmed alsothat life performance of lead storage batteries using the grids isimproved and the breakage rate is reduced. Furthermore, it has beenconfirmed that the configuration in which the recess of the valley 4 bis in a range from 30% or more to 70% or less is particularly effective,with attaining the highest effect in the case where the recess is 50%.Moreover, it has been confirmed that the effect is further enhanced byforming the inward inclined face 4 d in the peripheral side face of thevalley 4 b.

As apparent from the above description, according to the grid for abattery plate of the invention and the method of producing it,deformation of the endmost node of the metal sheet can be reduced byrecessing the peripheral side face of the endmost node forming valley ofthe endmost disk cutter. Therefore, the wires drawn out from the endmostnode can be surely prevented from being easily broken, a failure of abattery can be suppressed from occurring, and the life of a battery canbe prolonged.

Preferred embodiments of the invention have been described.

The invention can be implemented by combining the various processesdescribed above to prevent rupture from occurring during a productionprocess, to prevent corrosion and a crack of corrosion from occurringafter production of a grid for a battery plate, thereby preventing thecapacity of a lead storage battery from being reduced, and the life ofthe battery from being shortened. As described above, the aspects of theinvention relate to one another as a whole. These inventions belong tothe same technique from the viewpoint that a crack of corrosion in anode of a grid which may occur during a process of producing a grid fora battery plate, or during use in a storage battery can be preventedfrom occurring so as to provide a storage battery of a long life.

1. A method of producing a grid for a battery plate comprising:providing a rotary expander for forming a large number of zigzag slitsin a metal sheet having two or more opposed disk cutter rolls, each ofsaid disk cutter rolls having: a plurality of disk cutters on a sameshaft with forming a gap therebetween, each of said disk cutters beingconfigured by: alternately forming ridges in which a peripheral sideface protrudes toward an outer periphery from a referencecircumferential face of a predetermined radius, and valleys in which aperipheral side face composed of a face substantially extending alongsaid circumferential face is formed, in a whole periphery of aperipheral edge of a disk, said reference circumferential face beingcentered at an axis of said disk; and, for each of said valleys, forminga groove which is opened in a peripheral side face of said valley, in aperipheral edge portion of one of disk faces in which said valleys thatare adjacent to each other via a ridge are formed in an oppositelyreverse manner, wherein: in each of said disk cutters, an inclined faceis formed in each of said peripheral side faces which extend from apexesof ridges formed on both sides of each of said valleys to said valley,said inclined face more approaching the axis as being nearer to said oneof said disk faces in which said groove of said valley is formed; andpassing said metal sheet between said two or more opposed disk cutterrolls.
 2. A method of producing a grid for a battery plate according toclaim 1, wherein said inclined face is formed from a position of each ofsaid peripheral side faces of said ridges, to each of said valleys, theposition being higher than said valleys by one third or more of a heightin a radial direction of said disk cutter, said height extending fromeach of said valleys to each of said apexes of said ridges.
 3. A methodof producing a grid for a battery plate according to claim 1, wherein aninclined angle of said inclined face is substantially equal to orsmaller than 40 degrees with respect to the reference circumferentialface.